u/crrpit has a few thoughts on this matter that are relevant, and so do I. (Credit is also due to u/Libertat, as I pillaged some of their thoughts in a private discussion we had some time ago for some of the below.)

So let me lead off by listing my complete and utter lack of qualifications. I dropped out of college after two years in, my degree was in Language and Literature, and the two history classes I had were basically just high school-level history classes set in university and the only thing I learned from there was what a 'mandala state' was. I am most assuredly not a historian by any definition, not even by crrpit's third option listed above. I am most accurately someone who knows about the topic listed in my flair, and who knows more about it than 90% of people on Reddit.

The difference between me and a capital-H Historian (by any of crrpit's definitions above) is in training, methodology, familiarity with scholarship, access to resources, and a bunch of other stuff I'm no doubt missing.

For the specific purpose of AskHistorians, or for talking to people generally, the difference is not really much. Wells are wells no matter who's telling you about them. They really did still drink water in the Middle Ages. I am very likely a bit more informal than the historians would be, but the quality of information is largely the same.

Except.

I have a lot of limitations that the above purpose doesn't show. I'm lucky that there isn't a lot of controversy in my field. The same cannot be said for some other fields - for instance, the debate about How Hoplites Fought, or just what the hell happened to the Western Roman Empire in the late 400s, or whether or not the 30 Years War was about religion, or any other discourse I'm not familiar with (which is likely A Lot), or or or...

Because I'm not tapped into the current academic consensus in my field, I don't know what's happening. This isn't much of a downside for me, as my main mission is just to kill a myth, but if I were a touch more serious in my study, it would be. It means that I'm behind on a lot of things. I don't know what Roberta Magnusson, Paolo Squatriti, or Mark Stoyle are academically doing right now, if they'll publish something I might want to read, or have any idea what direction their research is taking. I don't know how to keep in contact with them or their research. Magnusson could come out tomorrow with a book that upends everything I have and I wouldn't know about it until next yearish if I was lucky.

Related to this, I also don't have the same access that a historian does to primary and secondary resources. I got my bibliography by asking around, and I can mine the bibliography of the books I have. But again, I'm not tapped into the scholarship. I know exactly zero primary sources except for those mentioned in the books I have. I don't even know how much access I have to archival material. Yeah, I know the financial records of Exeter going back into the Middle Ages are available at the Devon Records Office - but if I were to ring them and ask to see the rolls, I don't know if they'd let my non-qualified ass into the archives.

I'm also not trained in the historical method. I've picked up quite a lot of tricks from hanging around here, but I still know where my limitations are. This is why I don't do primary sources. Pretty much all history derives from studying primary sources, but you have to know how to read them, how to use them, how to put them into context. And I don't. I know where some primary sources are biased (Jordanes simps for the Goths, Polybios is a stooge for Scipio Aemilianus and his family, Liutprand of Cremona spent half of his Byzantine embassy whining), but I don't know how to pick through a primary source the way a trained historian would.

What I am is a guy with too many books, enough time to read through them, and enough spite against common Pop History Understanding to make killing a myth to be my life's work -

but no, even past all that, I am not a historian.

EDIT: I don't even have JSTOR access!