Yes, that’s what causes the trouble. I think recently discourse published an option to enable unicode in usernames (https://meta.discourse.org/t/unicode-usernames-and-group-names/117737), but not sure if @anoek plans to enable those I guess it might come with other issues or some plugin conflicts.
We cannot really change your username as it is linked with your OGS nickname. If you so wished you can change your username on OGS game site (or have a moderator do it) and then logging off and in again here should update it.
But not sure it is worth the hassle… And sorry about the trouble.