Hi @Starchild, we’ve discussed this issue at Changing email subject line should start a new post . On that topic, I shared a workaround for changing the subject.
I also linked to the discussion I’m having with the Discourse developers. Infuriatingly, the founder replied, “This is rather intentional at the moment. … If someone wants to start a new topic, they should send a new email.” I made a case for how it’s the wrong behavior, but the founder checked out of the conversation.
In any case, I should be able to eventually address the problem with a plugin. If anyone wants to help develop it, please let me know!