> If the comment was the reference to a banned member, was the action actually inappropriate?

Yes

> why the heck would you make a comment that could derail a discussion.

Banning the poster derailed the discussion even more. So much so, it made it to front page of HN.

I am not arguing they shouldn't have banned Guido because of who he is; I am arguing banning anyone should have a pretty high threshold, and when it happens it should be done with extreme transparency. Asking to wait for a member to join the discussion later about a relevant topic shouldn't come anywhere near that threshold.