Did pirates really make people walk the plank or leave them on deserted islands?

They absolutely did leave people on deserted islands. "Walking the plank" though, that's more sketchy.

Part 1: Marooning on Islands

Firstly, the islands. Marooning was a punishment that was prescribed in almost all pirate articles of the early 18th century. Here is an excerpt of the pirate John Philips' articles from 1723:

II. If any Man shall offer to run away, or keep any Secret from the Company, he shall be marooned with one Bottle of Powder, one Bottle of Water, one small Arm, and Shot.

Ironically, John Philips did not remotely follow his own articles as he violently forced captured sailors to join his crew and when some of his crew attempted to escape, he simply murdered them in cold blood rather than marooning them (I discuss this in more detail in this post).

However, pirates did sometimes maroon crew members or prisoners they wanted to get rid of, but they weren't the only ones to do so. Regular non-piratical merchant ships would sometimes maroon crew members for special offenses, namely homosexuality. A notable instance of this occurred in 1725 when Leendert Hasenbosch, an employee of the Dutch East India Company, was marooned on the remote Ascension Island in the middle of the Atlantic after being accused of sodomy. He was given some supplies but slowly died of dehydration over about six months after failing to find water. In 1728, two Dutch cabin boys accused of sodomy were taken and left on separate islands in the Houtman Abrolhos archipelago off the western coast of Australia without food or water and almost certainly died (the Dutchmen who left them there were themselves shipwrecked elsewhere in the archipelago at the time but they at least had water).

As for pirates, the pirate Edward England was marooned in 1720 by his own crew along with three loyalists on the island of Mauritius in the Indian Ocean. The reason was because his crew was angered by England's leniency toward prisoners, in contrast to the majority of the pirates who wanted to kill and torture them. After some time on Mauritius, England and those marooned with him managed to built a boat and sail to Madagascar where they lived at some European outposts for a while. The Scottish privateer Alexander Selkirk was famously marooned on the Juan Fernandez Islands off the coast of Chile from 1704-1707 after he complained about his ship's unseaworthiness, but he lived relatively comfortably in the temperate climate, being initially supplied with a gun and shot and being able to live off the island's many wild goats.

Other times, pirates would maroon prisoners on sometimes very inhospitable islands with very little supplies or no supplies at all, sometimes even naked. One instance of this occured in 1718 which I detail in this post but I'll quote here:

"In October 1718 there was a mutiny of former pirates aboard three small ships in the Bahamas. One of the captains joined the pirates after having been overpowered but the two other captains refused and some others of the crew did as well. Some of the pirates wanted to kill them but they eventually decided to strip them naked and put them onto a nearby island in the Bahamas called Green Turtle Cay. The next morning the pirates invited them back on the ship promising to give them clothes, but instead they beat them and forced them to reveal where some valuables were stored. Afterwards they put them back onto the island still naked and sailed away. The castaways tried to repair a damaged ship left near the island, but after five days the pirates returned and were enraged to find them attempting to escape. The pirates chased them across the island but they hid in the trees and undergrowth. The pirates quickly gave up but sank the ship they had been trying to repair before sailing away again. Now the castaways survived for another eight days on berries and shellfish and fish they could catch, but were unable to even light a fire to cook with. Then the pirates came back again and sent one man to call them and promise them food and blankets (to use as clothes since they were still naked), which they did give them while they stayed on the island for three days before departing again, leaving five men on the island but keeping the two captains with them this time. The castaways now survived better than before having been secretly given a tinderbox to make fire by a forced member of the pirate crew. When the pirates returned yet again they hid but the pirates left more supplies for them, including muskets with powder and shot for hunting. Four days later the pirates returned again, burned down the hut they had made and then left again. This time the pirates were captured by Spanish privateers and then revealed where they had marooned the five men and a rescue ship was sent."

In another incident very similar to the above, in 1730 the Englishman John Cockburn was marooned on a small island off the coast of Honduras with a dozen others of his crew after being captured by Spanish pirates along with one pirate who had a falling out with the rest. Cockburn managed to swim to the mainland with the former pirate and they made their way along the coast and fell in with illegal English logwood cutters who lived there. Cockburn’s account was published in his book The Unfortunate Englishmen: Or, a faithful narrative of the distress and adventures of John Cockburn.

Also very similar to the above incidents, a century later Spanish pirates marooned the American captain Barnabas Lincoln with his crew on a small sandy cay with a few mangroves off the coast of Cuba in 1822. They suffered extremely from thirst and hunger and insects and their attempts to escape by building a boat were unsuccessful and eventually one of them died, but fortunately they were rescued by a ship after three weeks. Lincoln wrote a pamphlet about this and an edited version can be found in the book Captured by Pirates: 22 firsthand accounts of murder and mayhem on the high seas by John Richard Stephens.

Another prisoner of the pirates, Philip Ashton, wasn't marooned but he did escape and run away from the pirates on the large uninhabited tropical island of Roatan off the coast of Honduras in 1723. He survived there for sixteen months in a pretty miserable condition before falling in with local English logwood cutters and eventually being rescued by a ship. He later published an account of his time as a castaway and this is detailed in Edward E. Leslie's book Desperate Journeys, Abandoned Souls as well as Gregory N. Flemming's book At the Point of the Cutlass: The pirate capture, bold escape, and lonely exile of Philip Ashton.