The quality of posting in the main section of the forum has dropped dramatically since I joined. Nothings going to change unless paid signatures are stopped though (and yes Im aware that Im wearing one but I dont post like the spammers present there).
Well that means you're okay with the paid signature campaigns but just wanted them to be spam free. It's not as same as you saying they should be stopped completely. If you were any serious, you'd not be wearing a signature at all. That's a good first initiative.
I think merit requirements for signatures are a step in the right direction. It forces users to actually create posts which are valid. This would have to be maintained w/ strict rules regarding merit, and strict rules against merit abuse.
Having been on this forum for more than 5 years, I will admit I have seen a drastic decrease in post quality. Thinking back, bounties weren't really a huge thing, and I think with their increase, and signature campaigns, it was only going to get worse without a further mod presence.
While I think that signature campaigns are affecting this, I don't believe they should be prohibited. But I do believe a "minimum merit" rule should go into effect. IE, signature campaigns can only add members who have a minimum amount of merit per rank (as some campaigns have effectively put into place).
The only other thing I can say is to not let the spam make you avoid that category. Stay in the category, post high quality posts within the category, and report all posts you can.