I find its Tapas format that keeps me from commenting.
With a single to 3 page uplaod a week style, there isn't much to say about the pages on there own, unless one in particular stands out. I'd feel more comfortable with commenting like at the end of a chapter after I've had the chance to go through a full plot of a chapter and take everything in. I think I'd perfer for people to comment once a chapter has gone through, and tell me their thoughts on a chapter to chapter basis, or cover page to cover page.
I watch a good couple of manga reviews, its chapter by chapter, which I'd feel more comfortable commenting about. If I just want to overall comment that "I like your art style" or liking the comic in a general way, I'd be more likely to comment on the feed than the pages.