I'm not sure what level you have to be at to get the ability to Flag stories. I do know that using it too much will get it turned off for you (as that happened

I'm not sure what level you have to be at to get the ability to Flag stories. I do know that using it too much will get it turned off for you (as that happened to me). I had been assuming that Flagging stories was the right thing to do (as they don't have downvotes, and we're told not to comment negatively on them), but apparently you can have too much of a good thing!