Linux to the rescue!
Long story short, Comcast uses an application called Sandvine to disrupt certain BitTorrent traffic. That is to say it’s not always Sandvine preventing your from seeding “distros,” but sometimes. Using the old standby iptables firewall, you can configure your system to, in layman terms, “defeat” the Sandvine nastiness.
Best of all, what you’re doing only affects your BitTorrent port, so no need to fear “messing up” your entire Internet connection.
All that’s involved is modifying a few values, so if you speak Linux, have Comcast and want to improve your BitTorrent experience, give it a shot and let us know how it turns out. I have Cablevision, which doesn’t seem to have as many seeding issues as you Comcast guys do, so I try it out.