Unfortunately that would require a major rewrite of the present comments system (which I'm not averse to, but probably won't happen in the current Perl codebase as its just not worth it - the shelf life of the perl codebase is limited). The problem is that the comments are all tied into the first entry for that day - they know nothing of any subsequent entries. Indeed, making them aware of that would require an 'Add Comment' button after each individual entry, which as you can see isn't present.
The comments system needs a darn good overhaul :) I'll certainly bear it in mind for the new software - which has been a long time coming I know - but it really is being worked on now (when I'm not working on new features for the existing code base)... Indeed, some 'privileged' people have seen the first steps so they can confirm it really is happening at last :)
Steve.