I dislike that. IMO, if the content cannot stand on its own, it did not need to be posted. A comment that adds something to it, to initiate a discussion, is fine. But a comment that just says what that post is? That is neither interesting nor engaging.

Such comments also encourage the idea that people "own" the threads they start. I've seen people get mad when people take the conversation in a direction they did not want, or add instructions telling people what to talk about and putting constraints around discussion. Such things stifle interesting conversation.

So I land heavily the opposite direction. Just post, and leave it at that. If the community finds it interesting, discussion will ensue.

Now, Show HNs are their own thing. An initial explanation is absolutely appropriate for a show HN. But it should be part of the post, not a comment.

Even so, not sure it qualifies for flagging