What is a Poe?

[FatAndFaithless]

It's a reference to Poe's Law:

Poe's law is an Internet adage that states that, without a clear indicator of the author's intent, it is impossible to create a parody of extreme views so obviously exaggerated that it cannot be mistaken by some readers or viewers as a sincere expression of the parodied views.

So for example, if someone comes to this forum and acts ridiculous, spewing horrifyingly bigoted and insane religious views that seem over-the-top, they might be called a "Poe" as in they're faking it for effect. A Poe pretends to believe wacky things, but the hard part is telling if they're really faking it or not, hence Poe's law.