UPC has a similar system, where the guest network has extra bandwidth, on top of your own subscription. Even if Comcast doesn't do this, he is leeching off his neighbour's connection and not his own.
Was interested in this so I did a bit of investigation into whether it makes sense with UPC.
UPC only makes a small amount of bandwidth available on the 'Wi Free' (UPC's version of Xfinity) network, seems to be about 2.5mbps down and 0.5mbps up. In my country (Ireland), the minimum package you need to get 'Wi-Free' is 120mbps down, so It's not really worth the effort for an extra 1% bandwidth.
UPC only makes a small amount of bandwidth available on the 'Wi Free' (UPC's version of Xfinity) network, seems to be about 2.5mbps down and 0.5mbps up. In my country (Ireland), the minimum package you need to get 'Wi-Free' is 120mbps down, so It's not really worth the effort for an extra 1% bandwidth.