Ahh, this old chestnut :)

This is - to be frank - a conspiracy theory, and is taken about as seriously as the "switch". The answer is probably more valuable if I explain how this became a story.

First thing's first, yes Titanic had a coal fire in stokehold 9. This was pretty common and while cause for headache, it certainly wasn't cause for concern. It wasn't going to spread anywhere- it was encased in steel of course. It required prioritizing that stokehold, so shoveling the coal out first so it didn't spread and waste precious fuel (Titanic was also sailing during a coal strike so it really was precious fuel), then you'd soak the culprit embers, then you'd clean up the stokehold, and then you'd move on. Was it annoying? Absolutely. Was it dangerous? Hardly. Titanic's coal fire was well contained and out by noon on April 13th. Plenty of ships sailed with them and you never heard about it because they didn't become famous. That's the story. Not very exciting really, is it?

So how, and when, did this become a story? It initially appeared a few days after the sinking in the desperate rush of a press overwhelmed with Titanic news and spread throughout the country- and in fact, we may even have the culprit!

Here's the Fergus County Democrat, Lewiston Montana, April 30th 1912.

FIERCE FIRE RAGED: COAL BUNKERS OF TITANIC SEETHED WITH FLAMES FROM TIME OF ITS DEPARTURE

The White Star Liner Titanic was on fire from the day she sailed from Southampton. Her officers and crew knew it and they had fought the fire for days. This story, told for the first time today by the survivors of the crew, who were sent back to England aboard the Red Star Liner Lapland was only one of the many thrilling tales of the first - and last- voyage of the Titanic.

"The Titanic sailed from Southampton on Wednesday April 10th at noon", said J. Dilley, fireman on the Titanic...From the day we sailed, the Titanic was on fire and my sole duty, together with 11 other men, had been to fight that fire. We made no headway against it.... No sir, we didn't get that fire out.... but we didn't need much help, it was right under bunker 6 that the iceberg tore the biggest hole in Titanic.."

Thrilling! What an account! Let's break it down!

1. "The story, told for the first time today"- dated April 30th. Except it wasn't. This article was a reprint, it had been appearing all over the country. We have it in the Topeka State Journal from April 22nd, the Stevens Point Journal from April 27th, and and the Syracuse Herald from April 20th which added "He further declared that seamen had fought the fire during the five days that the ship was racing westward on her maiden voyage and that the highest speed was maintained on this account."

Let's look at that last statement- Titanic wasn't speeding (she literally wasn't capable of it) and she certainly wasn't at "her highest speed maintained". Titanic never reached her highest speed, and she certainly never maintained it. Even at the time of collision, she had yet to finish lighting her boilers, and certainly they weren't run in enough to get her cruising at top speed.

Ships don't work like that. You can't get a brand new ocean liner, fill her full of coal and barrel her across the North Atlantic. Her equipment is brand new and it has to be eased in. This takes multiple voyages. Had Titanic lived, she would have eventually hit- and even exceeded- her top speed (her sister Olympic was able to cruise comfortable at 23/24 knots when she got older) but it wasn't going to happen on this voyage. Those boilers and turbine engines weren't anywhere close to being run in- they were literally brand new.

2. "We made no headway against it.... No sir, we didn't get that fire out"- yes they did, it was out on the 13th of April. It was tiny.

3. "it was right under bunker 6 that the iceberg tore the biggest hole in Titanic.." - Well that's nice but the coal fire was in bunker #9, although to be fair, he may have meant boiler room #6 which was fed by bunker #9. Either way, this is also odd testimony because the iceberg didn't tear big holes in Titanic (although at the time, that's what everyone assumed had happened). The iceberg sheared rivet heads that caused plate separation along about 300 feet of Titanic's starboard side- estimates totaling about 12 square feet in total damage.

Now, boiler room 6 was absolutely hit, we have the testimony of stoker Barrett and engineer Hesketh who describe being hit by seawater before escaping #6 as the watertight doors shut. But, how Dilley knew that this was "the biggest hole" when there were no big holes, nor, I'm sure, did he sound the damage (if he did, he probably wouldn't have made this statement or even survived), is a mystery.

Or is it? Because just deconstructing that statement, we know that Dilly is at best- hyperbolizing- or at worst- lying. Either way, he's factually incorrect. Whether this was his brain reconciling what he experienced with the wildly inaccurate newspaper reports, or whether he just wanted to tell a good story- I don't know, but as I cited above, the story got picked up and run across the country for the rest of April.

So, it seems we may have our culprit, Firemen J. Dilly, also known by his real name Mr Christopher Arthur Shulver (he lived quite a...umm...colorful life). He was, ironically, killed by an explosion in a coal bunker on the Adriatic.

So that's that, and the story seemed to die for almost a century. The press post Titanic was filled with half truths, rumors, inaccuracies, and just shoddy reporting. The public was hungry for information and the newspapers were desperate for answers and they started printing everything as news- a large amount of it verifiably false, but some which was annoyingly stayed around.

So, why did we pick up on this of all things? I can give you my opinion- it's because to this day, Titanic is remarkably sell-able, especially after the absolute obsession with Cameron's film and the demand for Titanic material in its wake. This meant that authors had to find a new way sell old material- and the way to do that is to publish conspiracy theories and make a lot of money off renewed public interest. This is where the "switch" theory began, and this is where the coal fire found new life as well.

Most recently, a documentary aired on the history channel which dredged this up again. Their big proof was a photo which supposedly showed the massive coal damage to Titanic's superstructure. What they failed to tell you, however, is that the "damage" is nowhere near stokehold number 9. It's way too far back and way too - hilariously- far up on the hull. #9 was forward and below the water line. This photo was a smear amidships and up around C Deck. If any damage did exist, it wouldn't be able to be seen anyway.

So what was the smear? Well the documentary conveniently forgot to mention that Titanic was being painted right up until she departed. They also claimed she was carrying 2500 hundred people-- which she wasn't, she was carrying 2200.

But it was made, and it aired, and people viewed it, and money was made. Titanic is always going to be of interest, but unfortunately, there's only so many ways you can re-tell the same story that everyone knows, and you don't want to go into the boring history because the other version is so much more interesting (she was speeding through an ice field!). And that's where this comes in.

That, of course, is all my opinion. The facts, however, are that the coal fire was a minor and common annoyance. Coal fires burned on ships smaller and less sturdy than Titanic. They just never became famous :)

I hope this helps!

To add a bit onto u/YourLocalTitanicGuy's post, here is an image that shows the position of the coal bunker relative to the "mark" Senan Molony basis his documentary on. The bunker in question is purple while the "mark" is black. I will state I've also seen historians debate on whether or not both starboard side bunkers flanking Watertight Bulkhead "E" were ablaze. As you can see, the mark is a good distance from the fire, actually it's on the Mail Room on G Deck and 3rd Class cabins on F Deck. Here are the deckplans, but be warned, the controls are very wonky.

The "mark" Molony has focused on so much is likely a shadow cast onto the hull as a result of the sun reflecting off the water onto her curved bow.

That picture also shows the damage we believe Titanic sustained from the iceberg, shown in the form of green lines.

I think that image alone shows why the basic concept is wrong as well. Titanic had sustained damage along her 5 forward compartments that ensured they would flood much faster than the pumps could handle, meaning she was going down no matter what. Even if we were to accept the fire weakened that area of the hull, it wouldn't have made a difference seeing as the majority of the hull forward of those bunkers also failed.

I want to point out something that, as YourLocalTitanicGuy said, puts Senan Molony's coal fire documentary on par with Robin Gardiner's switch conspiracy. Molony's documentary claims Harland & Wolff's Chief Draughtsman, the famed Thomas Andrews, gave a much more generous time initially before changing his mind later on in the sinking. It makes the connection this is because of Watertight Bulkhead "E" failing.

All I have to say there is there is no evidence Andrews said anything other than they had at most, two hours reportedly shortly after midnight. That's as soon as he was able to compile the necessary information and process it into a prognosis. The documentary effectively claims there was undiscovered testimony regarding the sinking of the Titanic from one of the most important figures involved.

If I may direct my attention to the article you linked in the OP, it doesn't make reference to professional historians, but to a member of the British Titanic Historical Society. More insultingly, it offers up the mummy's curse and a U-Boat attack as "counterbalance." This is the Smithsonian, which I assumed held itself to higher journalistic standards.

I can't really address the rest of the recent version of the coal fire theory without making a really long post as it takes on so many other things. Things such as Titanic was made of inferior materials, the crew was acting abnormally in regard to their navigation of the ship, coal fires were immediate grounds for cancellation of a voyage in 1912. Etc Etc.

EDIT:

My apologies, I am a fool. I forgot I had previously posted an excerpt from "Report into the Loss of the SS Titanic" by Halpern et al, 2016 edition. I think this book would have been printed the same year as the documentary, but I cannot be sure if this is a direct confrontation with Molony's theory.