I'm going way off topic here,
since what I'm now posting has nothing to do with freedom of speech.
Around TR (and most web forums I've been to), trolling is usually reserved for posts intended to start a disagreement. It often includes minimal participation by the discussion starter or original poster, and it's assume he or she started the fight so he could then sit back and laugh at everyone sniping at each other. This doesn't require untrue statements; just tossing out a reasoned, informed opinion is often enough; see many 'Windows vs. Linux' discussion.
I don't know that we need another word for 'liar'. As to moderators banning a troll, today's troll on one topic may be tomorrow's informed voice on another. Yeah, repeat offenders should be banned, but only after a pattern of offense. And remember, many panels aren't moderated at all.