I think the main problem would be policing / verification.
I sometimes have one in my signature, but I wouldn't necessarily be against what you propose. Mind you .. I don't think anyone could complain that my posts lack tangible content! lol .. I may have only been around a couple of years, but I'm likely already at least top 5 in terms of my percentage of the NamePros database in pure file size .. lol. I'm curious if there's anyone (with over 100 posts) that have anything close to my "characters per post" ratio?
What actually bugs me in a similar way of people developing "fake forum authority", is the countless "likes" in the welcome threads that people get sometime just for writing "Welcome to NP". In fact I'm convinced most people only post welcoming messages there just because it's super easy to up their like count.
What I find super entertaining is that despite my always trying to post longer welcoming messages with actual content .. and more specifically with actually content related to what the original posted actually wrote .. that some people seem to deliberately not give me a like, while giving others with a 12 character reply a like! lol
Similarly with likes in the "domains you bought in ..." threads. Just because someone posts a good domain is not the proper reason to give them a forum like. Forum likes should be based on bringing actual value to the conversation. If someone post a domain they bought and explained the reason for it, then even if you don't think it's a good domain, it could still be appropriate to give a like if as part of their reasoning for buying the domain, they explain some concepts/ideas that could be helpful to others.
Anyhow .. to get back to the point .. the real issue with the signatures then becomes .. can Bob Parson come become a member and technically be the only person allowed to post GoDaddy affiliate links in his signature? lol
I say GoDaddy because it's fairly obvious, but there are hundreds of smaller registrars out there whose ownership not only is unknown, but could actually be private. Same goes for the various domain services out there. Policing would unfortunately be a nightmare.
Forums are dying..Facebook (other big social media sites) are replacing forums.
What planet have you been on? lol
.. Forums HAVE BEEN dead for a decade. I had what was once the biggest DJ/Club music community in the world for a couple of years at the start of the millenium, and indeed it was eventually social media and namely Facebook that totally killed it (and 95% of other forums out there) ... but the irony is that now in turn FaceBook is dying. It will never completely die .. but the average person spends far less time on FB today than in 2008! Can't really compare "page views" with all the scrolling, but average time per person is likely a quarter of what it once was. I actually see forums in general returning to some degree .. facebook ironically makes it almost impossible to have a quality community of any reasonable size .. forums still are the only alternative for that.