I think flairs would be the same as user-tagging. There’s an open proposal for post-tagging github.com/LemmyNet/rfcs/pull/4 and the discussion there was so far to add tagging for one type of thing and then later expand to others (like user tagging).
It’s a bit of a complicated feature because it needs decision who can tag whom, and what is the scope (who is it federated two), and how does it transfer / interact with other ActivityPub software.