One feature that might be fun as a plugin (can’t see this as core) – when it is your birthday, show a cake Emoji next to your name.
Reddit does something like this “cakeday” and it’s fun. But we could use two possible dates:
the day you joined that Discourse (default)
your actual birthday, as entered in a custom birthday field in user profile, since we don’t – and have no plans to – have this field by default
Anyway I think this is a fun feature and would make an excellent plugin.