Unrelated, but I just found a post which was “Automatically Deleted by Timer”. This is a housekeeping function of Discourse to prune empty topics after comments are moved/merged to another topic. Somehow this timer got set on the new topic I created from @Nesslig20’s RNA World comment.
This topic timer isn’t visible to moderators (not in our control), and it is separate from the timer that automatically closes comments. I will ask at Discourse Meta if there is some admin setting for this. In the meantime I’ll try to pay more attention to new topics created from moved comments.
I when through several years of the Deleted Topics log looking for “lost” topics, and restored one other that should not have been deleted.