clang-format and 'clang-format on' and 'clang-format off'

Can the 'clang-format on/off' trigger be indirected into
something non-clang specific via a macro?

Not every project is going to use only the clang-format tool.

Why? The end goal would be to enforce all code to be running under the
same formatting rules (which, in practice, means the same tool at the
moment).

Note that you can use clang-format with most editors (including vim,
emacs, VS, VSCode, XCode, Sublime, Atom...).

Cheers,
Miguel