Wikimedia Bugzilla is closed!

When a user registers a new name, if the name is too similar to that of an
existing user (e.g. only one or two letters changed, such as RickK -> RicKK), it
should be disallowed. We get far too many impersonation attacks, and some of
them are quite subtle, e.g. the infamous lowercase-l vs. uppercase-i trick, or
tiny accents on letters.

Possibly check each letter to a set of variants (which would be the same letter
with different accents) and consider those the same for this purpose.