How important are reddit-style flairs for people? There's the raised issue https://github.com/LemmyNet/lemmy/issues/317 which has it listed as a far-future, with questions as far as how to handle federation.

Personally, having at least an initial implementation done on a community level would be largely sufficient, with expansion to instance-wide being optional. The situation I've found most useful, personally, is sports-related groups with your favored team being your flair. This gives context to comments without constantly having to say "as a X fan"