So think of each instance as a mini reddit. lemmy.com/c/funny is not the same comunity as lemmy.org/c/funny but you can subscribe to both or one or neither.
Likewise your username is unique only on the instance you joined so there might be another Kritical on a different instance.
Yeah we do, JWs mostly. But if you look at the /m I mod you can gauge the response they get from me ;)