If you can no longer comment, one of the following usually applies:

Community ban

You may see: "You can't comment here because you are banned." This means your account has an active community ban. Check any ban notice at the top of the site for the end date.

Creating ban

A stricter ban blocks creating, downloading, publishing, and commenting.

Rate limiting

If you comment too quickly, you may be temporarily blocked with: "Sorry, you're doing that too much." Wait a few minutes and try again.

Comments disabled on a specific creation

The creation owner may have turned off comments for that item. You will see "Comments have been disabled for this creation."

Blocked user

If you or the other person has blocked the other, commenting will not be possible on their content.