Since when has this been a thing?
This has been a thing even before you registered on this forum
You signed up in late 2014 and here is a post in 2013 where someone says how to use it
If it annoys you, just install ad-block and make a rule for the signatures to block them. Since only a couple of people do it at the moment and they do it with very distinctive colours and codes this should be easy.
No need for that.
Profile -> Look and Layout Preferences -> Don't show users' signatures.