That 100 views/0 replies thing has never happened to me, but I saw it happen to someone recently and she bumped it up after it hit 121 with 0 replies. It made me think- they weren't bad at all. Even some were great. She had posted a bunch of wedding ones, maybe 8 or so total.
Usually I only post 3 pictures max because that's how *I* feel will raise my chances of getting CC. When I see posts with 10 or more pics, I close them usually. Unless its like elsaspet's wedding photos or something fantastic.. then I will usually comment.
I have noticed that I tend to comment more when I see outstanding work. I feel more enthusiastic to say great job, those are excellent or so on.
I also will comment more if there are one or two pics that I know I can positively critique.
The ones I don't comment on are the straight up average or not sensational. Like not anything technically or compositionally wrong.. but nothing spectacular either.
However, I did just post 1 picture recently and its got 9 or so replies now, but 4 of them are me commenting also. But it has 179 views! I think I am trying to learn to take that with a grain of salt.