_identifiers in BRS?

What’s the situation with identifiers starting with underscore in BSC?
Seems to work just fine:

BrightScript Debugger> _h = { _2: 3 }
BrightScript Debugger> ? _h._2
 3

But the documentation says otherwise:

Identifiers (names of variables, functions, labels, or object member functions or interfaces (appear after a “.”)) have the following rules.

  • must start with an alphabetic character (a – z)
    I am hoping for confirmation that indeed, _names are safe to use and documentation is behind.