This is not a big issue, but did come as a surprise.
There is an answer I posted to a question about a mountainous planet: What would produce the most uneven but earthlike planetary surface?
A kind gentleman added a comment pointing out I'd not discussed earthquakes in this scenario. So I added a comment saying I would, then edited the question. Some short time later, both comments had disappeared.
I imagine that someone noticed that interaction and removed the now-unnecessary comments -- they'd done their work -- but I just wanted to make sure that that was the custom.
Oh yes, the actual question... Is this expected behavior?