Yes as well as pissing off the RP community and being flat out ignored.
Only if you're shit at it. A lot of people are very open to someone joining them as long as they don't try to throw imaginary authority at scenes they aren't a part of.
"Hey, is there a problem here?" goes a lot further than "HEY STOP OR I'LL ARREST YOU."
Thanks for making a link! I'm posting on my phone from work which is a struggle. Too many RPers think that can attack or bully other characters right in public and that nobody should bother them and there's no NPC guards in Ul'dah. It makes it unsafe for nonviolent characters that don't want to just blacklist everyone they don't like. It's good to have someone around to stick up for people.