I haven't done much open source contribution, but it seems like we should be able to write some kind of flagging/filter system to check if PR's are quality. One-liners and comment modification? Highly suspect. Although I am not sure what GitHub offers as far as PR management API.
Just from what I am seeing on this Twitter, it seems pretty clear that there are some easily identifiable patterns. i.e. "Amazing". - https://twitter.com/ryan_southgate/status/131164593596180480...
I could be just completely out of touch with opensource.