Tested. This idea was in fact useless.
It didn’t work, because when viewed from far away, e.g. a character’s face might no longer have sharp edges, so it gets all blurred. Also, objects may actually bleed a bit, because both the pixel inside the object boundary and its neighbor outside it trigger the edge detector. For inking, this doesn’t matter, but for blurring…
Thresholding parameters could be added, like for inking, but I think that smoothing of the light/dark boundaries shouldn’t require that much careful tweaking from the user. The lighting space approach is cleaner in at least two ways - the smoothing range is a more transparent parameter to configure, and that approach doesn’t require a postprocessing filter (leaving more buffers and registers for other filters).
I’ve also added the TEXCOORDn allocator thingy, and now any combination of filters can be enabled at the same time (as long as the hardware has enough registers).
An updated patch will follow shortly.