I think it's a standard tool: trollish comments look like being ignored to the trolls. But I think it's impolite to delete comments made in good faith without notification and usable guidelines for cleaning up and reposting. (Hint hint.)

How did you work out that it had been deleted? Just by logging out, looking and trying to remember where you had stuff posted?

I only made one comment on the subject and I was rather confused that it was being ignored. I also knew I might have said too much about the Roko post and actually included a sentence saying that if I crossed the line I'd appreciate being told to edit it instead of having the entire thing deleted. So I just checked that one comment in particular. If other comments of mine have been deleted I wouldn't know about it, though this was the only comment in which I have discussed the Roko post.

I doubt that this is a deliberate feature.