You've highlighted the exact reason this is a problem for mastodon and not for bluesky: on the latter, there's a default, so people who don't realise why it mat

You've highlighted the exact reason this is a problem for mastodon and not for bluesky: on the latter, there's a default, so people who don't realise why it matters don't need to worry about it. For the record, there are other differences - on Bluesky, you use your non-default domain to login in exactly the same place, there aren't 'weird gaps' between different domains.