On the other hand, the forum's we don't moderate scams policy prevents him from meddling into what other people are advertising.
Yeah I'm well aware of that, but in both cases (banners and sigs) the end result is the same, forum has been used to advertise and promote scam.
I don't know how often people here talk about bitcointalk with other crypto enthusiasts (I do almost daily) and one of the popular answers I get when I ask why are they avoiding it is that it's scammers paradise where they can do whatever the fuck they want, which sucks but that's how part of crypto community perceives this forum.