I have now read Comcast's filings on network management
Assuming they are truthful (which I am willing to believe, I see no inherent to lie at this point and the explanation explains all observed phenomena), I conclude the following:
1) Comcast was not trying to engage in explicitly anticompetitive conduct wrt their video product. To the extent that was a motivator, it was merely gravy.
2) Comcast was being as stupid and lazy as possible in their network management practices. They made a corporate decision to use the most brute force, unthinking system for managing potential network congestion possible. This included (a) identifying the applications their traffic monitoring system told them was the most frequently associated with congestion and totally blocking those applications; and (b) picking off the top 1000 users per month by market area regardless of the actual state of congestion or total bandwidth used.
3) Comcast compounded this idiocy by a corporate culture based on (a) refusal to disclose, and (b) resisting all cooperation with the FCC as a matter of principle.
4) When pushed, Comcast could develop an alternative system that actually addressed congestion on a real time basis, targeted those users consuming the greatest bandwidth for sustainable periods, and did so in a way that did not terminate connections or disable protocols.
Conclusion: Comcast's real problem is its monopolist mindset. It recognized it had a problem and that the easiest solution would be the least popular with its customers. It went ahead and did it anyway, "solving" the problem by refusing to disclose.
Secondary conclusion: Comcast now seems to be investing serious effort in repairing its reputation in the market and with federal regulators.
Tertiary conclusion: Regulation works -- at least in the absence of a competitive market. Comcast bad doggy. Lie to customers. Smack doggie nose hard! No poop on customers! Bad doggie!