Ability to filter part of the CSS validation

Hi,

I saw in your FAQ that you cannot validate CSS with -moz-* properties for
example.

But most of time, these properties are used just to give a better user
experience for those who user latest web browser.

Why not include a way to tell the validator to filter all these properies?
For example, including a comment:

/* Do not Validate BEGIN */
 -moz-....
 -webkit-...
/* Do not Validate END */

or in the url which tell the validator to ignore all properies begining by
'-' such as -moz*, -webkit*...

http://jigsaw.w3.org/css-validator/check/referer?profile=css3&ignoreproprietary=true

But this are just example and I believe it should not be too difficult to
implement.
The advantage would be to provide a validation for CSS which use web browser
specific properties.

regards,
YE