Recently, I tried to speak to the NPCs in the Battlefields (early in the game). All I did have several damaged items repaired. When I left the conversation, I found that I was encumbered. Somehow, my inventory had gained weight, even though I didn't acquire any new items. My wife played around with this a bit and found that it happens when you have the death knight selected when you speak to the NPC. To avoid it, it seems that you have to use your main character to speak to those NPCs.
