Given this: > My router is an ISP provisioned one so the feature-set there is somewhat limited My assumption was that their router doesn't support disabling u

Given this: > My router is an ISP provisioned one so the feature-set there is somewhat limited My assumption was that their router doesn't support disabling uPnP for a single client, so it's 100% on or 100% off. If they play a significant number of p2p games or use p2p applications with non-predictable ports, it might well be more difficult to do manual port-forwarding when needed than to leave uPnP enabled (or even impossible, depending on what the router can do).