Ooh, you know what? I ran your the CREATE DOMAIN statement in your new test and pg_dump'ed that, and as far as I can tell the _name_ of the not-null constraint is not dumped either. So it's not just the comment that we're losing. That's a separate bug, and probably needs to be fixed first, although I'm not sure if that one is going to be back-patchable. Which means, I withdraw my earlier assessment that the comment fix is back-patchable as a whole.
-- Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
