They meant that it is a good blog post (likely - not specifically stated), but that when posted on HN, will likely inspire bad comments. I interpreted your comm

They meant that it is a good blog post (likely - not specifically stated), but that when posted on HN, will likely inspire bad comments. I interpreted your comment as conflating the concepts 'post' and 'submission' - the difference I saw was that I read 'post' with a non-HN context (a post on an external website), but submission with a HN context (specifically, a submission on HN).