I don't have an answer for the last question, but the easiest thing to do is this: make a shortcut on your keyboard (mine's the 'L' key) with the /loot command. Anything that comes up can be looted. If nothing does, then nothing can be taken from that person or NPC. I have found this to be very useful sometimes.
Now, when I was playing a couple years ago, we weren't able to loot or thieve from live players, and actually, 99.9% of anything having to do with thievery hadn't been integrated into the game yet. I don't know how it is now (I just started playing again) but we couldn't loot other players' kills, either. What seems to be the same is the randomness of when and what you get from looting a kill. The harder a thing is to defeat, the more money you can cash in on its treasures. BUT there is no real predicting if you're going to get a fish or a gem-studded short sword.
