Instead of venting heat, wouldn't it be more efficient not to produce it?
You are right about the lack of thermal conductivity in space, but the problem with venting heat is only an issue when systems are running and you are actually generating heat.
I mean, if you have 500 people shoved together in a tin can in outer space, wouldn't just their body heat pose a risk of pushing the ship to dangerous interior temperatures if heat isn't vented somehow?