I would love to have some general advice on dealing with passive-aggressive people -- particularly those that are peers. So much of their bad behavior resides in comments that SEEM okay on the surface, but the tone or something else about it tells you that they are being weasely. Another observed behavior might be "throwing people under the bus." For instance, waiting to out an issue until it's in a large group meeting of peers or in front of a business partner instead of having a one-on-one discussion.
I realize the answer might be "feedback." The problem I have with this particular personality type is that they are snipers. I'm either left wondering what they REALLY mean or I'm speechless at their rude and unprofessional behavior.