I used to moderate one of the minor cat picture subs. It had those problems too, but I managed to use automderator to remove 98% of it. The head mod was one of those people with dozens of subs who ignored them, so I was able to get away with doing that. Once in a blue moon the head mod came there and liked the spam being gone. My guess is that those other cat picture subs have head mods with dozens of subs who just don’t care.