While the Mastodon #ipv6 only experiment was fun, I saw no point in sticking to the barricades for much longer. Perhaps at some point a dedicated instance to it have to be set up.
So I have reinstated proper html handling, removed the "HTTP 410 Gone" reponse and once again added the A-record to the DNS.
The speed in which posts are now appearing in the timeline have now increased considerably.
A private and experimental Mastodon server. This server only accepts IPv6 connections, please pester you local admin if they still do not have IPv6 available.