This is not a duplicate of Why are usernames allowed to be composed entirely of non-visible Unicode characters? as that simply asks why this ability exists. This is a feature request asking for this ability to be removed. This answer by former employee @waffles doesn't really apply either; while I do agree that some problematic usernames can only be detected by humans (especially when they depend on context), this type of usernames can be blocked automatically.
Consider this post.
It's made by a user who decided to put some strange characters in their username, which results in them not being rendered. Where can you click to navigate to that user?
It took me a while to realize you can click the (blank) avatar as well, I've never used that feature before.
I propose to disallow usernames like this; there should always be something of a name to click on. I mean, it's called a 'display name', so it should be ... displayed, right?
The characters are from the Latin-1 Supplement, alternating between a LATIN CAPITAL LETTER I WITH ACUTE (U+00CD) and a SINGLE SHIFT THREE (U+008F). The first one is unusual but rather innocent (just a vowel with a diacritical mark), the second one is 'suspicious' in as far as Unicode characters can be like that. The Unicode code point is still visible in the URL, encoded as
%cd%8f%cd%8f%cd%8f; their username has been reset networkwide by an unknown ♦ moderator (whoever it was, thank you!).