Hi OP,

A username will appear if a username has been set - it's only anonymous if a user doesn't yet have a username. There isn't a way to thank anonymously with a username. This isn't something we're able to change at the moment, but we are discussing user feedback about how this feature works.

If there are quite a few 'thanks' notifications, we would group them together to keep things tidy - but if you click the thanks button on your post, it will open up with a list of users who have thanked you.