The forum is nearing the lowest point content-wise I have seen. Click on just about any thread and it is mindless replies and bumps from people with big signature ads pushing something. There is nothing here, no content, no dialog. It is certainly not the place for cryptographers and programmers and entrepreneurs to exchange information about Bitcoin. If you are lucky, you will find someone completely out of their depth asking a stupid question answered a hundred times, someone that then cannot understand the answer.
There is no reason or need for a signature. Limiting the BBcode to higher-activity members helped the look of the forum, but just creates a market for old accounts to do the spamming.
What is needed is to deincentivize this crap posting by completely removing the signature. End the signature campaigns and the pay for obnoxious scam sites. People are profiting from posting nonsense and making this forum useless, and this is seemingly the only way to make it stop.
Then we have the activity/post count chasers, which you can see from dozens of "why isn't my activity going up" posts. There's another number that can just be removed from posts. Take away that incentive to post junk also.
You are right on some things. For example when you write: "If you are lucky, you will find someone completely out of their depth asking a stupid question answered a hundred times, someone that then cannot understand the answer." There are to many threads when you can meet such things.
But you are wrong in having fear from these people. Their never, according to me, enter in threads when the discussion is about questions regarding "cryptographers and programmers and entrepreneurs" which want to "exchange information about Bitcoin".
So it was enough for you to eliminate the "easy" threads which are the preferred ones for that kind of people and you are safe.
Fortunately the forum has to many boards, child boards, and threads. Everyone of those has its content well defined and its name write clearly on it. You choose those which interest to you and if your interest are particular I can assure you that you not find any post with signature campaign there.
The signature campaigns are not the fault and the cause of your problem. Their target are never such boards or child boards for which you talk in your post. Or even if there are people with signature campaign who write in such places I am sure that those understand well those and want to tell their thoughts in those. Which, I think, cannot be crap. If someone dares to write in those, that meaning that he cannot be an crap author. It is another thing if someone spam there. But their posts can be reported and he will banned from the forum.
I think that who have something with the signature campaigns are you. And what is the reason of this ire that it is known only by you.