>The _VFP is a VFP COM interface. It's a bug that you can add a property to it.
>

I don't agree.
Every object has Application, and therefore it is a lot of profit and sensible to be able to add properties to the application object.
Besides it is difficult to think to a bug or a side effect that supports,
(almost!) all the commands without collapsing or errors.

ADDPROPERTY(_VFP,"SomeProperty",4)
odelegate=CREATEOBJECT("_VFP_Delegate")

BINDEVENT(_VFP,"SomeProperty",odelegate,"callMe",1)
_VFP.SomeProperty = 5

DEFINE CLASS _VFP_Delegate AS Custom
	PROCEDURE callme
		? "bind",this.Application.SomeProperty
ENDDEFINE