The message is generated by bbPress as an alert on the WP dashboard. Some explanation here:
https://codex.bbpress.org/features/tools/upgrade-forums/
Thanks for that heads-up.
Thanks, Robin. While I’m not expert in manipulating databases, it should be possible to create a command that selects all users for whom the number of posts is zero and deletes then en masse. As it happens, the command for deleting users isn’t functioning properly on my website: I can delete one at a time, but if I select multiple users and hit delete I get an error message. Until I get that fixed, I can’t use the normal process for user deletions to solve this problem.
Thanks, tried that to no effect. Dashboard shows Topics and Replies but not Forums.
Thanks so much for the quick and helpful reply. I thought I was missing something in settings . . .