silverpill, It's official now: Threads implemented FEP-e232
https://engineering.fb.com/2024/03/21/networking-traffic/threads-has-entered-the-fediverse/
Article contains a couple of minor inaccuracies:
_misskey_quote
doesn't build on FEP-e232, and the other property name isquoteUrl
, notquoteURL
. But overall it's good and I hope other implementers will notice it.