EDIT: UNOBTAINABLE NOW
A lot of people, including myself have been having difficulty being able to post comments to dynasty wire stories, with the issue seemingly being server side. Be cautious of this when you attempt to start this game as you will NOT be able to complete this game to 100%. No announcement of server closure has come thus far, but I (along with others) have had problems posting comments in NCAA Football 12, 13 and 14.
How to attain the achievement
You can get this achievement WITHOUT buying the Online Pass. EA amidst all their douchebaggery did give a 2 day free trial for everyone who plays the game, which is more than enough time to get this and the photo achievement.
Go into Online Dynasty and either start your own or join into a non private dynasty. Once in the dynasty click 'A' on the "Dynasty Wire" hub, which will take you to a screen with all the stories for the week on it. Click 'A' on anyone of those to leave a comment, once your comment is posted and the dynasty is saved the achievement should unlock. Make sure you save the online dynasty to your HDD or MU because if you don't the achievement does not unlock.
After you get your achievement you can continue playing if you wish, but if you just joined for the achievement, then navigate over to the 'Commish Tools' hub if you created your own dynasty and select the retire option. Otherwise go to the hub to the left of 'My NCAA' hub and select retire.