Removing signature globally will kill this forum from having visitors.
No it wouldn't despite how much you want to believe this...
Nobody knows for sure what would happen in that case, but I think it is very likely that forum traffic would decrease and that it would go somewhere else, like Roger Vers forum.
Some traffic would remain here for sure but Im far away from thinking the overall result would be wonderful, and I also think if Theymos hasn't taken that measure yet it is because he thinks something similar, otherwise he would have taken it a long time ago.
Of course traffic would decrease hugely and people would flock to the next best thing but it wouldn't kill the forum. The forum will still be here and it will quickly turn into a utopia compared to what it is now. There's plenty of posters here who don't have or ever intend to join a signature campaign and in fact many of the best posters don't have a paid signature at all (DannyHamilton etc). I'm sure theymos has taken into consideration the huge effect banning signatures would have on the forum but he has also stated signatures will likely be the next to go in the merit system fails so for those thinking they'll never go I wouldn't get too cocky.