I think that pictures of rust trouble areas should be mandatory in the for sale section. Just like adding a price and location. Look at every thread. Everyone is asking the same question. I don't think there are any exceptions to this. It would really streamline things.
You already can't post a car for sale without underbody pics. Let's just make it official.
I was interested in a car on here recently and the seller was either clueless, a horrible photographer, or both. The seller advertised the car as completely rust free, but in one of the terrible pictures you sent me you could clearly see that it was a mess.