[texhax] commands within sections in multi-author document

[Karl Berry]

    redefine \newcommand so that it is only active within each TeX
    section.

Sorry for my ignorance, but how about simply enclosing each section
within \begingroup ... \endgroup?

Failing that, the other idea that comes to mind is to define a new
\newcommand which makes its new command name unique by adding a suffix
based on the section number.