This is the first time I've seen it in my HN Replies, but I have seen "* * *" before on https://news.ycombinator.com/. I even saw another comment asking about this type of comment.
Edit: I truly did not believe you, but it appears to maybe be the “delay” feature [0]. Users with a delay set might show the asterisks until the delay passes.
And I've seen it in 100% of your replies to me, when I've never seen it for other replies. So I wonder if it's related to how you use HN