The problem is the genre of the snarky dismissal. Perhaps there was a solid point behind what you said, but you didn't express it that way.

It's a tragedy of the commons. Posting such coments never feels harmful, but once they get above a certain level the whole community becomes filled with toxic fumes. This threshold is lower than it seems—the damage isn't only in the fumes your comment gives off, but in the encouragement it gives others to do the same.

Tragedy of the commons plus broken windows theory is not an auspicious combination, so we try to be proactive about asking people not to do this.