[pm24601]

What aren't you doing while you are going off and being a super hero?

Are you disobeying your manager's direction? (And thereby undercutting their creditability/authority - and how does that make the manager appear to their supers/peers?)

Why can't you go to your manager and ask for permission? If not, why not?

How would you feel if your "great" rewrite is rejected - because someone else was already doing the rewrite; or because the system is going to be redesign entirely? (For example, the code will be ported from .NET to Java - and all the .NET code will be discarded)

If you haven't yet, try being a manager for a while and then see if you still think that this sort of troublemaker.