To me, the whole comfort level of the situation is driven by how people react. If the naked goes out of his way to cover up, it adds tension. Similarly, if the clothed guy either stares inappropriately or unnaturally looks away, that also adds tension. Whether I'm the clothed or the naked guy, I just carry on at ease, as if we were both clothed or naked. If I'm the naked guy, I'm likely to stay naked. It's a locker room. If a shower full of guys just saw my dick, it seems a bit silly to cover it for someone i know. If my body language conveys i'm fine with it, the other guy usually is, as well.