If a dispute arises between two users that cannot be resolved via normal communication, cast a custom moderator flag and explain the situation in detail, and a moderator will... moderate the dispute.
FWIW, code changes are a disputed topic. I feel pretty strongly that users really shouldn't be modifying other people's code at all, but some users feel it is OK if the person knows what their doing and makes their intent clear. Jeff Atwood always viewed Stack Overflow as a big source control system, and wasn't bothered by any form of collaborative editing.
I'm not, however, impressed by arguments that code should follow all best practices, and that editors should feel that they have broad permissions to modify other people's code so that it satisfies their sensibilities for what they think best practices should be. If you strongly feel that another answer is inadequate in this way, the remedy is to post your own answer.
Nor do I think editors should get into edit wars over semantics like this. Moderators do not moderate answers based on their technical veracity, but they can, and will, take action on edit wars. If you feel compelled to change someone else's working code, and they roll back your change, just let it be.