Would it be more sanitized?
Would it be less filled with spams?
Would there be fewer alternate accounts?
everything is not necessarily also the case. but what is very likely to happen is the reduced activity of many accounts on the forum. not all of them are in the forums and creating posts to achieve the weekly targets of the campaigns they participate in.
even without a signature campaign, there will still be accounts of many members who will still be actively discussing on the forums. but as I said, the activity will probably decrease.