CSS filter hacks and validation

Has there ever been any discussion on some method for hiding 'invalid'
selectors from the CSS validator.
For example there is a -moz-outline which if i am not mistaken does not
validate but is a nice feature which will become the outline property. I
would like to be able to use some of these temporary features untill
CSS3 is implemented and still have my CSS2 validate.
 
shaggy