Oh, I see how it works: you (Tibby) get to decide who is a bad poster.
(*) In Tibby's judgement, poster A is "bad" => poster A is "bad".
But, wait! Tibby has declared that poster Tibby is "bad"! We need a postulate:
"Statements predicated on the judgement of "bad" posters are meaningless."
But now, attempts to apply (*) to ANY poster are meaningless, since Tibby already applied (*) to himself, and so by the postulate, (*) is contradicted in general.
The question becomes, then: because we cannot attempt to discover whether or not Tibby is a "bad" poster by his own assertions since doing so necessarily leads to a contradiction, how will we ever know for certain that he is bad poster?
I think we need a second postulate:
"A poster is said to be "bad" when s/he continuously makes logical errors, even after s/he is aware of such mistakes".
Tibby says he is a bad poster. Therefore Tibby knows his posts are "bad". But Tibby continues to post, without first rectifying his habit of making "bad" posts. Therefore, by the second postulate, Tibby is a bad poster.
Okay, I've "proved" that you are a "bad" poster, and also disproved your previously supplied proof that I am a "bad" poster.
Care to try again?