NPM will complain if one try to publish an package with the same version number as a previously published package:
Example:
npm ERR! publish fail Cannot publish over existing version.
npm ERR! publish fail Update the 'version' field in package.json and try again.
Reggie silently publishes the package and overrides the old version. In my humble opinion I think Reggie should follow NPM on this. Its very easy to forget to up a version number when publishing and if its forgotten its good that the registry complains.
If this is a wanted feature I can take a stab at it and make a pull request.