No subject

A conforming implementation may also include additional
functionality that does not prevent running code written to rely
solely on the profile as specified in this standard. For example,
it may provide additional classes, new methods on existing
classes, or a new interface on a standardized class, but it shall
not add methods or properties to interfaces specified in this
standard.

So, for instance, if on mono somebody made the Object class
implement a MonoSpecificObject interface, as far as I know the
mono .NET implementation would still comply with the standard.

Of course, this would not necessarily be a good idea, and it
would not make you identify the platform, but only the CLI
implementation...

Probably the right thing would be having the necessary facilities
for platform identification included in a future revision of the
standard.

Ciao,
  Massimiliano