Well, since TMann has already mentioned my name, I suppose I can toss my hat into the ring.

I can grind a stub or italic on any nib you have, as long as it'll produce a result at least 0.3 mm wide. Any narrower than that doesn't give sufficient line variation to overcome the effects of capillary action, and there just isn't enough line variation to be useful. At the other end, I've ground italics as broad as 1.5 mm on retipped nibs.
For me, the appearance of a pen's nib is important, and I take extra steps to ensure that the result of my regrinding will look as good as it can within the constraints imposed by such things as the material and plating of the nib. Here are a Levenger True Writer that I reground to a cursive italic and a Columbus Academia that I made into a stub.

Appearance is important, but the shape of the tip is even more so, and here is where I see a lot of problems caused by people who don't actually understand what they are trying to accomplish. Anybody can make a nib smooth for a very limited range of hold angles and altitudes, but it's more difficult to make a nib that will work properly under the range of conditions imposed by most people. (The difference is that a properly ground nib lets you work, while a badly ground one
makes you work -- its way.) This is a Pelikan M800 that came to me for correction after a "bargain" nib worker had made it into a "cursive italic." Left is before I worked on it, right is after. Note the damage the previous person did to the slit with a really crude knife job.
