I don't think so. If you could, then anyone could come along, copy the source code, and reverify it with completely different comments, which opens up for all types of attacks, including phishing. You could possibly contact Etherscan directly and they might let you replace the code if you can prove that you're the creator of the contract.
I guess you can't do this. Because etherscan will check your deployed contract byte code with current submitted code(compile version of byte code), if booth are same then only they will save your code to etherscan db.
Why they are doing:
Contracts are immutable, once contract is deployed in eth network you can't change.
Competitor/hacker can copy the verified code and change your comments and resubmit your code. That may leads some more complications.
Better contract etherscan.io team. For explain the issue for change req.