Unfortunately a pretty common spam/annoyance online is putting "spam"
via abusing Unicode symbols - which is used for multilingual support -
in display names. This typically results in an unreadable word jumble in
our UI, which looks bad.
So I decided to put a stop to that by clipping some labels that could be
used for this crap. I didn't cover *everything* yet, but this at least
prevents these idiots from showing up in the completion menu, the room
member list and as authors for messages.
