If they have access to your IP addresses and can send them on where they liked, I'd say that was a potential concern. Not to mention that some people may have PMs they'd like kept private. At least you know who's nominally responsible for it on BG and can form a judgement. It may be imperfect but, this guy, who knows? It could be Gary Glitter.
I can’t imagine Bart in platforms, but possible I suppose.
I reset my router regularly, I’m on dynamic IP, so less of a concern for me.
If I need to send confidential PM’s or talk about the upcoming cultural revolution etc, I go to Skype or a different platform.
Honestly don’t give two shits about who Bart is or isn’t.