I would be grateful, if you could explain which of the guidelines I may have transgressed. I read them all and searched "grammar". Nothing comes to mind.

My own comment was precipitated by the sneering tone I read in (sic!)

Which itself points out a grammatical mistake unnecessarily. Then compounds this, by making a more egregious mistake.

Really my comment was making the same point. Don't point out grammatical mistakes, which is the precise purpose of (sic).