I noticed that a post on a topic was deleted so I investigated and found it had a null for user but was obviously valid content from a legitimate user.
I then marked the post as undeleted but since I had no way of assigning it to a user, it kept the null user field. This was a bad idea, since now the topic is unreadable.
How did the post get a null for user?
How to fix so users can see the other posts in the topic?