For the record, my current hypothesis is this:

If Comcast's DHCP server thinks my MAC address has a lease from it and I start sending out discoveries that are asking for 192.168.100.10, those discoveries are ignored. They shouldn't be, because Comcast's Cable Modems hand out that address, and gateway devices might obtain it during a power outage that is shorter than the leases that are handed out by the real DHCP server.

I could be wrong about this. Its just a hypothesis based on the information that I have and I don't have any way to test it. But its pretty reasonable.

Getting Comcast to investigate it is impossible. I can't get them to accept the facts that I can prove with packet captures, so getting them to consider a hypothesis... it ain't gunna happen.

RE: Comcast's DHCP is broken