Indeed. Many suits are two layers of leather in the knees, elbows and seat. Still very uncommon for the first layer to burn through in a slide but it does happen once in a great while. I was actually just talking to a friend about his last track incident, at about 100mph, and he did say that as he slid he turned himself over because he was getting hot from the friction!
I have talked to several guys that didn't like 3/4 length jackets becuase they tend to get pushed up in front when sitting on the bike. I think their issue was that they had to get it big enough to fit around their gut which made it loose around the chest/shoulder area.
I finally tried a 3/4 length "Sliders" brand kevlar mesh jacket that I used on my big trip this summer and I noticed that I had to be careful when first sitting on the bike, but otherwise I didn't notice any bunching up.