Does it make sense for these Topic to continue to exist?
Topics like this can be reported or moved to Archive and moderators can decide what to do with them later.
I don't see any issue with them still existing, but I would like if members had the option to delete or at least hide their topics from public.
How does the forum deal with a person's right to be "forgotten"? Imagine that a user wants to delete all his activity from the forum, is it possible?
User can currently delete all his posts (except topics) and ask moderators to change his user name.
Even if someone manages to deletes all his posts and topics, there is still several archives recorded for everything that was ever posted.