It's not just NBCSN that has PQ issues.
On MSNBC there is extra macroblocking that appears during animated transitions that happens on FiOS and Direct TV.
There has to be an issue with how the channels are being encoded by NBCU Comcast.
This post in DSLReports form talks about the PQ and compression of the NBCU Comcast Channels on FiOS,
Virginia Beach, VA
Got another update. NBC Universal is over-compressing the USA / SyFy / Bravo feed they are sending Vz (now being sent so all 3 can fit into one QAM). They have been notified but have responded that no other provider has complained. So, Vz has to convince them that it is an issue and keep work on getting it fixed."
If this is true then NBC U is compressing their MPEG2 channels to fit three into one QAM space for Cable TV.
Anyone know if they have plans to switch to MPEG4?