The Oilify plug-in dialog has a checkbox which enables/disables use of the 
"intensity algorithm," unchecked by default. 
 
In practice, when the intensity algorithm is not used (and we are in RGB mode), 
the resulting "oil painting" image gains numerous stray colors around the edges 
of normal color areas. 
 
Example: http://www.iskunk.org/tmp/oilify/oilify-trippy.jpg 
 
I submit that the checkbox is superfluous, because what you get when it is 
unchecked has little to do with the plug-in's stated purpose of making an image 
look like an oil painting. (Unless the purpose is to get a "bad acid trip" oil 
painting.) My suspicion is that this feature is exposed because the 
non-intensity-mode algorithm (oilify_rgb()) is simpler, was implemented first, 
and was never removed after its more advanced counterpart (oilify_intensity()) 
came to be. 
 
I think that the plug-in would be better off without oilify_rgb() and that 
checkbox. If removal of those is not feasible, however, I would at least 
suggest making "Use intensity" checked by default. The results, I think, are a 
closer match to what users would expect.