The photo ranking system still feels a bit random to me. Sometimes I'll take 2 nearly identical photos with significantly different ranks.
I think part of my general difficulty in getting high ranking photos is that I'm used to looking at photos in terms of artistic composition as compared to what I assume is more of a straightforwards scientific/ecological perspective that values clarity of subject over most else, but even aside from that I have a hard time figuring out what precisely the system is looking for.