You folks might just be time limited on the reply - HN puts some brakes on "too fast" commenting
See my profile if you want, that was my first comment in hours. I think it is that sort of brake, (prevents heated discussions veing quite so quick-fire) but it's not on the user, it's on everyone for <'5 [or something] minutes ago' comments; drcongo's happened to be '0 minutes ago' when I loaded the page, so I clicked on it to reply.
(I had to do it here too.)