Well, judging from the Errant Signal video, a lot of characters you meet have a bit of baggage to them, but you only ever really hear about it, you don't see it. One character starts drinking heavily at some point, for example, but there never really is a "god, he's drunk right now" moment - he just carries a bottle. And there's one moment when you can be an ass and stare through a keyhole to watch a character in the bathtub, and even enter. That could have been expanded into a more personal relationship, especially considering other involvements of the character in question. Sadly, it didn't have any bearing on the playthrough, though.
I'm going for the silent assassin approach, though at times I reload my saves a LOT just to explore a bit and take alternative ways of beating a room. Though I do try to take everyone out instead of ignoring them entirely - just non-lethal.