Comment 14 for bug 412928

I don' understand your objection

It's only a matter of doing automatically what you could do by hand

1) Create base shape (or group)
2) Draw a rectangle that encompasses the base shape. [Set it to no fill and give it a stroke you can see.]
3) Draw the "hole".
4) Select the rectangle and the hole, then Path > Difference to create the clipping path.
5) Select the base path and the group, then Right Click > Set Clip.

So applying an inverted mask would require inkscape to automatically do step 2 & 4.

And the svg would still be perfectly legit.

But I don't know if this is what the patch is really doing

So if the patch is just setting a custom attribute to tell the inkscape renderer to invert the clip path then I agree it's not the way to go