It also plays with the edit pencil on the title when you do it. So yeah it is an issue with allowing unicode characters, but don’t know if others would also break it. I’d suggest using a whitelist rather than a blacklist.
I am ok with allowing admin to pass it through a regex and adding a site setting.
Building a whitelist of every unicode that is valid and known to man is not easy, also zalgotext may be “valid” in your local its just that its overdoing it.
I don’t think this battle can easily be beaten by computers. Its why you have a flag button.
Really there is no problem with allowing the unicode in the title, you just need to separate the title from where the NEW alert bubble and edit pencil go. Surround the title in span or whatever and put them next to that.