Is "revert the damage" possible? If yes, is it too official?

Can "revert damage inflicted" be used in a letter to a friend? Would it sound too official? If yes, what phrase would you use instead of the high-lightened one below?

Not only did he type all kinds of nonsense and clicked on "Sent" button a few times on that page, he even tried browsing some others forums where I am a member and "provided some input" there too. I did punish him when I came back, but punishing him didn't revert all the damage inflicted.

You typically repair damage:

repair (verb, trans.)

• fix or mend (a thing suffering from damage or a fault)
• make good (such damage) by fixing or repairing it
• put right (a damaged relationship or unwelcome situation)

^{(New Oxford American Dictionary)}

The "revert the damage inflicted" may not be a most natural phrase, but is certainly grammatically acceptable and would be understood.

In this particular context, I would probably use undo. (Note the other minor changes, which are required for grammatical and logical correctness.)

I did punish him when I came back, although punishing him didn't undo all the damage inflicted.

You could also reverse the damage, if the damage is reversible. For example, if you broke my bicycle, I may ask you to repair the damage by fixing it, but if you put all my CDs in the wrong order, I may ask you to reverse the damage by putting them back in the original order.