Two questions regarding bags of holding. I assume there are no official answers to these (forgive me if there are), and I'm asking more for the sake of discussion than anything else.
1. What does it take to put something in a bag of holding? I assume they're not airtight. This raises a couple of problems. First: Why don't they have a pretty good air supply? There should be air passing in and out through the opening (though not a hell of a lot- but definitely some). Second: When a PC with a bag of holding enters a body of water, why doesn't their bag more or less immediately fill with water, ruining whatever's inside (as, of course, happens in Nethack)?
2. In a game where bags of holding and similar devices are relatively cheap, why are there often sewer systems of one sort or another? I'd think it'd be easy to use a bag of holding as a sort of bedpan, and empty it somewhere else or just discard it when full. Granted, it'd get a little stinky, but if we're really in a medieval sort of setting, I don't know that anyone would notice that much.