Now imagine that there is a new requirement of 10 merits to wear a signature, and multiply all this garbage x10 for an extended period of time. How does that sound? 
The 1 merit limit has reduced shitposting by 20-30% according to LoyceV's calculations here: https://bitcointalk.org/index.php?topic=5032314.msg46674375#msg46674375
Without any data we can't say for sure, but I think it's a fair assumption to say that a 10 merit limit would reduce spam by >50%. A week or two of spammers crying would be worth it for that. Then we might be able to hold a sensible discussion on BD again. Also, as per my other suggestion, a dedicated mod for the Meta board would go a long way to keeping things under control for those couple of weeks.