I don't know if you read Girl Genius, but there's usually some comment discussion in girlgenius_lair when each page is posted. Sometimes people will link previous appearances of a character who just showed up again, or link to other relevant past pages. (There's a feed, too, but I don't think people comment there. Maybe there are communities for other webcomics that also post the updates for commentary?)

I think seeing other people's comments is interesting, even though I don't generally comment myself. Go for it!