EDIT:
THIS SHADER WENT COMMERCIAL AND CAN BE DOWNLOADED FROM THE ASSET STORE.
(If you were lucky enough to grab it previously, you are free to use it anyway you want but i would appreciate your support if you buy it before using in a commercial product.)
Really Nice 
Donations accepted 
While I like the variation in the outline width, I still would like to know if it is possible to have a constant width outlines for the overall silhouette.
Like the outlines/edges around the arms are barely visible but the legs have quite a thick outlining, is it possible to have them of the same average width?
Its all about the difference in colors, as you see arms are blue as well as the background. If you make a difference there, you will see lines around arms as well.
If you want constant lines, its better to do it in object space rather than screen space.
You might as well try reducing the threshold to a very low value
ah so the outlines adopt their color from the neighbouring element?