Today, in Blogger Help Forum: Something Is Broken, we see a blog owner getting bad news.
I deleted a comment, but in the 'Recent Comments' gadget, it's still there! Help me!!This blog owner is about to learn about the "Recent Comments" gadget, in an unpleasant way.
The "Recent Comments" gadget displays the blog comments feed, for the host blog.
As soon as the comments publish to the blog, the feed is updated. Thanks to dynamic blog publishing, the next blog visitor causes the gadget to be updated with the latest feed items.
If the blog owner lets comments publish without moderation, and depends upon passive moderation (moderation by deleting unwanted comments, already published) to keep the blogs comments clean of unwanted content, providing any automatic display of the comments feed is just not a good idea.
As soon as the comments feed is updated, there's no known way to remove unwanted comments from the feed. If the blog owner lets unwanted comments get published, the blog feed is going to retain those unwanted comments - and there's nothing the owner can do.
This is yet another example why passive moderation of comments is just not a good idea.