Hi guys!
I _do_ see Derek's point here! His approach will make it easier to move away from custom icons in the future and integrate with freedesktop icons specifications, if more easily, once they are out the box. While the rendering works fine as is right now, I can guarantee, that the icons as they are will also be correctly rendered by librsvg. I've myself cursed librsvg for not rendering my icons properly, but it always has been a matter of gradients and transparencies within icons that at some point were created with CorelDraw. Text doesn't work either, but heck, this is nothing to care about for the inkscape icons. I don't think that the approach of handling over the icons to librsvg does definitely involve ripping apart the file. It might as well be possible to first extract them from the file into a temporary svg and hand this one over. Another advantage here would be that the icons will fade in with the rest of the desktop a little better. My theme is making use of icons having lower saturation and opacity in normal state, higher in prelight state and very low ones in insensitive state. Therefore even for markers and such, I'd make sense to have librsvg render them. Right now these preferences are not adapted by Inkscape, which is a pity IMHO.
Take care!
David