Interestingly, it seems to me that this definition would produce meta-maxims more readily than normal ones - "find out what your local society's norms are and stick to those" rather than "don't eat babies", for example.

Yes, it does produce meta-maxims in some sense. But meta-maxims can provide useful guidance. "Do unto others ..." is a meta-maxim. So is "Don't steal (anything from anybody)" or "Don't lie (about anything to anyone)"

As to whether this definition leads to the meta-maxim "find out what your local society's norms are and stick to those", that is explicitly not a consequence of this definition. Instead, the meta-maxim would be "work out what your local society's norms should be and set an example by doing that".