My fix on Primal and what needs to be fixed on Damus are two different things.

You can support reading old threads while support writing new replies using the new recommended part of the NIP-10 spec.

I looked briefly into implementing it in Damus a while back but it seemed like it was a non-trivial refactor requiring a lot of changes so I ended up not doing it. 

 @jb55 best of both worlds? But the extra work of supporting both might be a pain. I hope for a unified future. Past threads be damned, but if you can keep them that’s cool too.