@hongminhee it's no biggie - I doubt there's many projects that accept and thread correctly for this corner case - I just like to use this conversation as a test for threading. :D

Btw, I don't know if it's relevant to #fedify but I have the logic for threading (based on JWZ's old email threading algorithm) in the ONI project: https://git.sr.ht/~mariusor/oni/tree/master/item/src/js/items-threading.js

@moreal