Surprisingly there isn't any threads about this yet. I thought I would see a huge troll-fest of Paragon haters posting here.
Anyway, Paragon members who participated in the 25 man World First* kill of Sinestra have been banned for an unknown amount of time until GM's fully investigate the extent of the abusing by Paragon.
Lightnings Blade trade chat is being spammed by people threatening to quit the game because Blizzard want to cover up their own mistakes in the Sinestra fight development and blame Paragon for abusing the buggy mechanics.
Apparently Paragon abused a mechanic in the final phase of the boss fight to neglect all raid wide damage and turn the fight into a simple tank and spank. Obviously the full extent of it won't be apparent until an official blue post or until Paragon release the video.
Also according to a Paragon member who did not take place in the Sinestra raid but took part in todays Al'Akir raid has been saying in trade that they got banned when they looked like they were about to finally down Al'Akir after a few attempts. He is claiming that Blizzard don't want the raid content downed so soon so they banned Paragon when it looked obvious like they were getting extremely close to getting 13/13 progress. Apparently the ban took place when the boss was on 7 percent HP.
Expect an official update on Paragon's site soon and hopefully they get unbanned in time to get world first 13/13
EDIT* It was NOT for the DC Death Knight exploit.