Would have replied earlier, but IE crashed on this page (yet again...)
I think you can comment on any story if you click on the headline itself. However, this is not at all obvious, since the only indication that the headlines are clickable is a rollover. Using two different hyperink schemes (one of which violates basic usability principles) on the same page is an example of really bad interface design (from my viewpoint as a usability specialist, at least).
Also, for whatever reason, many of the stories lately are not showing up as having comments, even though they're there.