You can click on a post and go to "see user", which will show their user page. You could also add a signature to your posts -- they're more fun and personalized anyway. Right now that's manual effort, but i will probably add the ability to preset the editor with something so it's there every time you make a new post.

Usernames just don't work because they require an authoritative server to divvy them out. Ansiwave is designed to eventually be partially or completely decentralized -- all users are just ed25519 public keys, and the ID of a post is the signature of it, so there will never be conflicts between users/posts on different servers.

In theory we could one day have a decentralized way of registering unique usernames, similar to that DNS-like thing they made on ethereum. But i'm not even close to thinking about that right now.