Question: Do People Come Here To See If Their Fake Coins Are Passable?

I would say yes, of course, an Internet forum such as this can become a "university for counterfeiters".

Which is one reason why we tend not to describe all at once everything that's "wrong" with a fake ancient coin when it's posted. No need to help the enemy too much.

The really really good fakes, the ones that are impossible to tell just from pictures on the Internet, well there's not much we can do about those - unless we stop offering opinions entirely.

I would say a few probably do.
John1

There have been a few in the past. They got caught and the posts were removed, so do not go looking for examples.

I'm curious what the content of those trapped and removed posts generally is, and how frequent. My feeling (maybe without much to back it up) is that "there's a sucker born every minute" and these counterfeiters have plenty of customers as-is without going to the time and expense of making new dies just because a forum says a date or mint mark position is wrong for a certain coin. The percentage of real buyers who post somewhere first to confirm before buying a fake seems pretty low to me, so the market for the fakers is largely just making them "good enough." It does present a quandary for forums. If we don't tell them what's wrong with their coin, how are they going to learn to recognize the fakes?

True. While some are always seeking to improve their market share and profits by making better and better fakes, most counterfeiters, and certainly all their middlemen, aren't really interested in "improving" their product too much. Counterfeit coins don't need to be "perfect", they only need to be "good enough" to fool one person, once, and it's mission accomplished for the counterfeiter.

The "fraudulent use" that counterfeiters are far more likely to try to use a forum like ours for, is simply to give some kind of air of authenticity to the fakes they are already making. If they post a fake coin on a forum, and everybody's all "Ooooh, wow, that's amazing, super rare, worth thousands of dollars", and nobody is skeptical, then that's a counterfeiter's lucky strike gold mine. They can then post their fake coin for sale for a few hundred dollars, and post a link to that forum thread in their sale listing. People will read the thread and think they're buying a genuine coin for a bargain.

So it's always important to call out a fake, clearly and unambiguously, politely but firmly. Even for coins that aren't clear and obvious fakes, the possibility that it might be a higher-quality fake that can't easily be spotted over photos on the Internet should be aired, especially for new members for whom their only forum participation is seeking opinions on authenticity of their coins.

It has been my experience that the mass marketed counterfeits (gold bars, Am Silver & Gold Eagles, etc.) have intentional small differences from genuine items.