One idea would be to require a login but have a sub-forum for anonymous posts. That way the admins & mods would know who posted what but no one else would.
Of course, if someone wants to post anonymously, there are forums out there that allow that, in fact, "Onion" forums with hidden addresses, but I would avoid those, as there is quite of bit of evil things in the Deep Web (drugs, illicit porn, terrorism, etc.)
Of course, if someone wants to post anonymously, there are forums out there that allow that, in fact, "Onion" forums with hidden addresses, but I would avoid those, as there is quite of bit of evil things in the Deep Web (drugs, illicit porn, terrorism, etc.)