Obsolete in favor of 436475 right?

No, this is a part of 436475; it was proposed that we might prefer to insert a special kind of filter operation for box-reflect, rather than using reference filter path (which implies that it's an SVG filter, even though it isn't).

Purely a code clarity concern.

I'm switching off of paint. This doesn't seem urgent to me, but reassigning to that it has an owner.