Re: Rosetta is cool?
"How hot can Philae get?"
I dunno, but prolonged direct exposure to the sun with no intervening atmosphere means it can get very hot. As you mentioned, the lunar lander had a lot of gold "turkey foil" to reflect the suns rays and keep essential bits cooler. There's also the problem of dumping excess heat when the only method is radiation, again down to that inconvenient lack of atmosphere.
Then again, "hot" is relative. Boiling water (approx max. temp of the lunar surface) is only 63oC higher than our body temperature but it bloody hurts when you spill a fresh cup of tea down your pants! In space, stay in the shade and heat radiation means you'll eventually cool down to the background level of near absolute zero.