Prevent users from deleting Topics themselves?

  1. User registered and posted several messages.
  2. I moved some messages from one topic to a new one (offtopic/discussion).
  3. Message from the user from #1 was the first one, so he’s a “topic starter”. People discuss things in this new topic, 80+ messages.
  4. After several days, the user deletes his account. He can do that if the account is registered recently.
  5. The topic is deleted.

This is a real situation. I’ve found this topic because initially I thought the user has just deleted his own topic, but no — he just deleted the account, and that resulted in topic deletion. Discourse wipes all the account data (incl. all posts) upon deletion automatically — I see “topic deleted”, then “account deleted” in the logs.