This problem is easily fixable code-wise, but there's hesitation to diverge from the standards upon which Mastodon is based, and the original standards body behind this particular issue has long since disbanded. Other than monkeypatching Mastodon (and potentially breaking GNU social federation), the solution would be to re-convene a working standards body to implement a "correct" spec for this problem. Since nobody seems willing to do that, monkeypatching Mastodon to make an order of magnitude more users comfortable with switching to it is probably my recommendation.
The world needs more protocol standards bodies and more engaged, engineering-minded parliamentarians.
It looks like the Social CG is still active, and they're working on the new ActivityPub protocol which Mastodon 2.0 supports. Follower migration is one of the issues they're discussing:
This problem is easily fixable code-wise, but there's hesitation to diverge from the standards upon which Mastodon is based, and the original standards body behind this particular issue has long since disbanded. Other than monkeypatching Mastodon (and potentially breaking GNU social federation), the solution would be to re-convene a working standards body to implement a "correct" spec for this problem. Since nobody seems willing to do that, monkeypatching Mastodon to make an order of magnitude more users comfortable with switching to it is probably my recommendation.
The world needs more protocol standards bodies and more engaged, engineering-minded parliamentarians.