Right now, at the section level, it is not apparent which categories or discussions have "new" comments.  Once you get to the category level, there is a "last post" column, which is helpful... but other online discussion boards often have a bolded number or bolded button if there are new messages since the last time you logged in, etc.  For people with email settings "on" this is not a big deal, but when people turn that off, there is no way to tell if and where new messages appear....