This is the part that got my attention. My understanding is that deleting a user deletes all their message and lead to incomplete topics with “holes” in the remaining information on the forum. And it wouldn’t delete parts of the user’s messages quoted by other users, so the information quality would be decreased even more (and still could be linked to the user even after deletion if the user’s name or any other public information they shared was quoted by others).
Again, that’s what I understand but I could be wrong, and also I completely understand your concerns. 