“That is an ignorant thing to say,”, is pretty damn borderline. “Ignorant” is different than simply wrong.
However, note- that was a Mod Note and not a Warning. Notes are often given for something borderline but not specifically against the rules.
So, yes, OP, you are correct, technically you can attack the post , even calling it ignorant.
But What Exit, altho somewhat incorrect in saying "calling another post ignorant is violating the don’t insult others rule." But he was correct in giving you a Note for that post, which is clearly hoeing a very fine line.
What Exit should have said something like “calling another post ignorant is not violating the don’t insult others rule, but your post is getting very close to that line. Knock it off.”
So, the wording wasnt the best but a Note is exactly what that post deserved.
On another “note” (ha ha, see funny seque) how do we see any warnings or such (on our _permanent record") we have been given on this new board?
And can we please let warnings and special notes etc not be “permanent”? That’s just childish.