[atoav]

To add a little bit of context:

You know what I think would be way worse than todays reduced characterset usernames with some special rules or "just" using utf-8 for them?

Both. Imagine a world where some usernames are UTF-8 some are not and it is hard to figure out which is which. That would be worse than just leaving things as they are.

Avoiding that situation makes pulling the whole thing off even harder, since there needs to be a high amount of coordination between many projects, distros etc.