Its a bit of a vicious circle,
people leave nice comments (even if the image is crap) or don't comment on the image at all just so they don't offend you and you still go to there site.
I've had a long discussion with a couple of blogger friends about this. They wanted me to leave real comments, some critique etc.. on there images. I explained that if I did that 1. there other commenters might take the hump with me for not saying nice things and then stop visiting my site or 2. take the hump with me and then attack my images......
So its really a no win situation.
If you want critique on your work you won't get it through blogging, better to find another site for that and just enjoy blogging for what it is.