Current problem
There is no way for community or instance admins to block certain unicode characters or emojis in usernames and/or messages.
Proposed change
Add a community and instance-wide option for only allowing Latin characters, or any specific type of character, in usernames and/or messages.
Or only an option for disabling emojis.
Additional information
Random unicode characters can negatively impact accessibility to users reliant on screen readers.
Community/instance admins may also simply prefer their environment to be text-only.