Moving your account is the same as redirecting your account, but it will also irreversibly force everyone to unfollow your current account and follow your new account, if their software supports the Move activity. Your posts will not be moved, due to technical limitations. There is also a 30 day cooldown period in which you cannot migrate again, so be very careful before using this option!
Depending on if k/m/bin receives a "Move" activity, it may be possible to update user blocklists based on the information in the "Move" activity. However, "Move" activity is generally only sent to existing followers. (I don't know all the details on that) Activities are generally sent to an instance to handle, not individual user accounts, though, so I suspect this might not be as big of a hurdle as it might seem.
Short answer: Maybe. Depends on how they "Moved". It wouldn't be simple to implement, however I don't see anything preventing it in this particular case. You should open an Issue for feature request for it. I recommend including the above piece from the Mastodon documentation, however in your issue.
This is a result of the original design. Kbin, up until just before the peak traffic hit, was using boosts as upvotes and favorites/likes were just below the post/thread (where boost sits now). Lemmy does it the way it is now (likes = upvotes) so Ernest changed it to match Lemmy behavior. But just as he changed it, he hadn’t changed the calculation for reputation to match when the server nearly melted down and he has to spend all his time just trying to keep the site alive by himself.