I will double check things but it looks like a combination of a couple of things. Mainly, after posting your question you had a total of 2 reputation points (which would not give you permissions to comment, you need 5 points total). After accepting my answer, you receive 5 additional points giving you 7 (which means you are permitted to comment). The only flaw in there is that you gained too many points for accepting the answer (not a huge problem for us here but one i must correct in the module before a final release). For the record, you as the person accepting the answer should get 1 point (for taking the time to accept an answer), and I the answer author should have gained 5 points.