I found a possible issue with commenting: when I comment on a photo on my feed, the view returns to my feed, but the photo I commented on still has the old number of comments (if I view the comments, my comment will show up).

Might be a caching issue, but for consistency either the feed should be reloaded (slow), or that photo's comment count should be temporarily increased by one to make it correct (which should still be there if I comment on yet another photo before reloading my feed).