I revived our Guestbook using WordPress’s native comments in early June 2023. As of June 19, 2023, it has received many spam comments (no real comments yet). I discussed how I am using Comment Blocklist for WordPress to make filtering spam easier. In between updates (which I track using an ATOM feed), I save spam comments which make it through the blacklist and then add terms from those comments to my fork of the main repository (feel free to use). I then clear the deleted comments, usually using Meow Apps’ Database Cleaner.
On the morning of June 19, 2023, I updated my blacklist fork, merged my fork with the upstream repository, and then deleted my comments in WordPress with the Database Cleaner. However, I found that the comments were still displaying on the WordPress comments page despite appearing to be deleted in the plugin. I tried deleting on the comments page but the trashed and spam comments still appeared. I suspected the issue was our Redis Object Cache plugin, especially after it had once been behind a link styling issue. I flushed the Redis cache from the plugin settings. Sure enough, the deleted spam and trashed comments no longer appeared in the WordPress front-end.