This is in reference to Twitter comments from 2 years ago jokingly suggesting that based on the chilly reception from Gruber to any kind of reduction in ambiguity in Markdown's so-called spec... the name "YankeesSuck" could be used instead.
I understand that hackers tend to be irascible often, especially online, but parting shots like these are in very poor form. Consideration and goodwill tend be diminished when you can't be graceful no matter what the other party said. Especially considering that other party was originally the impetus for this in the first place.
You also have to consider the other party was subtweeting all day and calling people dicknoses.