Actually, it's not a bug. Particles are instances and are not calculated as real geometry. Therefore they are only really just a hot point. This was actually brought up during C4 and we were given the reason then. So, it's legacy code from C3. While the code can be totally rewritten to accomplish this, I don't think that it will move anywhere near the top of the wish list for awhile. Fluids and calculated fluid/particle dynamics actually use a completely different scheme. I'll be keeping this on my wish list. ;-)