Niels Möller wrote:
That is sane advice. But it is also an important part of the idea of the locally assigned numbers, that you are allowed to use these numbers in anyway you please, as long as you know what you're doing, and don't expect interoperability with other standards compliant implementations.
No "but".If you don't expect interoperability with other standards compliant implementations there is no reason to restrict yourself to using the range of locally assigned numbers in the first place.
The only reason for specifying a STANDARD way of adding locally defined codes and features to an implementation, is to make it possible for STANDARD implementations to inter operate even if they do not implement the same locally defined extensions.
Without this rationale there is little reason to reserve a space for locally defined codes.