Well I'm no expert in the area but apparently there's a thread dedicated to Comcast' Sandvine approaches here at dslreports' forums. Should shed a better light at things. Looks like a pretty mean-ass tech they're applying as well.
Basically DPI's and forged RST's to put it simply. Deluge had something which made it resistant (Az/Vuze and uTorrent had to peek through Deluge's source code to figure out what was the reason and apply it to theirs), but I'm guessing using the same logic, comcast must've looked through deluge's source code and adapted their settings or something....
Edit:I'm also in the SF area (San Mateo actually, south of SF) and I'm pretty much sandvined (0.0kb/s)...although my internet's been slow lately (3.5mb/s down, 0.5mb/s up, which is supposed to be (according to this idiotic comcast rep even though I've usually get 10.0mb/s down and 3mb/s up) 6mb/s down and 1.5mb/s) up.
Here's the thing. If you have Comcast, you can connect to other Comcast users. Anyone else, good luck. Your pieces never reach you, and vice versa, and are just routed back, making seeding nearly impossible. You cant upload. They throttle to no end. You're almost better off going with the dreaded dial up, then to go with Comcast. Dont wanna go too far off topic here, the throttling is an entirely different matter. Luckily, I dont have Comcast, but have I friends that do, with NO option for anything else, oher than AT & T, which is nearly as bad in certain areas .
"Dignity does not consist in possessing honors, but in deserving them."