I disagree with you. I am a member of many webmaster forums but its my first time to know to that "P.S = Postscript" and "IM = Internet Marketing". "PS" (not P.S) is used for Photoshop but never heard about postscript.IM usually means Internet Marketing when talking in a webmaster related forum.
as for PS I think it means postscript and not please see
P.s means postscript .
You forgot STFU ....
People use this when they are scammed.
thanks for the list, i just knew it will try to use