You can ask the mods here to have your account “anonymised,” which changes your BBS handle to something like “anon53666” on all existing comments. They also announce that they’ve done this in the General Moderation Topic so that others are aware the person has left.
BoingBoing apparently does this so that existing Discourse BBS comment threads don’t get eaten by the deletion of a user. The mods and admins can probably give you a more detailed explanation for why they handle deletion this way.
