In pretty sure it's not self promo to have a track in your signature. It doesn't really get in the way, ignore it if you don't like it
There's an option in the user profile to not display signatures. You can improve your own experience with that, at least.
I don't understand... No one is forcing you to click it, and this forum is all about music, it doesn't make a lot of sense to restrict it.Might as well remove the links in your profile as well, because it's no different.
As you can tell, I'm a quite active user on this forum. Embedded tracks in people's signatures have not hindered my ability to use this forum. It's pretty obvious which track are there for feedback and which ones aren't.
Flea markets and thrift stores are usually pretty easy to navigate, but I personally enjoy shopping at places with a little more class.