With new Jetpack release after WordPress 3.4 was released, Jetpack comes with some really good updates.
One of them is their comments handling. If you have enabled their new comment system and didn’t like what you saw you can choose to Deactivate the new comment system all together
Lets deactivate Jetpack comments step by step
First Goto Jetpack modules as shown below
Now once you are in then click on Learn more button on comments module as shown below
When you click on that button Configure button will change to Deactivate as shown below
Once you deactivate your Jetpack comment system you will receive the following message and the learn more button will become activate
That’s pretty much it. Your Jetpack comments systems now is gone, but you can always Activate it in case you want it back.
I hope this helps