I know this isn’t an answer but unless I’m using an end-to-end encrypted service like Element or Signal to communicate, I’m assuming anything I write in a DM will become public at some time. Given that, if it is something some sensitive, I will make sure to use one of those instead of the in-house DM.

A workaround is to add old. in front of the URL and you will still be able to use it, i.e., https://old.reddit.com/r/kbinmigration)