What you write sounds very good. If I might add one more idea...
When I start a private discussion, I often refer to content in public discussions. To do this, I move the mouse over a user name in a public discussion, click on the three dots and then "Send xy a message". Then the modal for entering a post opens and I start the private discussion.
Unfortunately I cannot use the reply or quote function in this situation, because when I try I am asked whether I want to leave the page (without the drafts extension) or (with activated drafts extension) my private discussion is - without confirmation - replaced by an empty reply in the public discussion.
It would be nice if I could simply quote from a public discussion inside a private discussion without having to open a second browser tab/window. I think it is safe to assume that what I am suggesting is the most likely reason for someone to quote or reply in this situation.
The same applies, by the way, when I move between discussions to pick up quotes from another discussion, so the problem probably arises from the Mentions extension.