Hi Kevin,

> Nevertheless, there's something inherently immediately
> intuitive about moving points "on" the curve,

Yup, and MoI allows you to move a point on the curve with this special drag mode that's mentioned here - that mode is active when you have control points turned on but then go and drag on a spot directly on a curve rather than dragging the control points.

See this post for some more information on how to do that:
http://moi3d.com/forum/index.php?webtag=MOI&msg=744.16

The part that does not work well for editing is not so much about just moving just one point on the curve, it's about moving a point on the curve while simultaneously locking down other various points on the curve into a fixed place as well.

Locking down a bunch of other points on the curve during the edit basically forces a pivoting action to happen around them, making a whole lot of bulges and ripples in the result.

Here's an example - say you have these 5 points here:



Now if you want to move the middle point but lock the curve down to pass through all the other 4 points where they currently are, you're basically forcing the curve to pivot around them like this:




It's really difficult to control things and maintain a nice shape when editing when there are all kinds of bulges being added into the curve like that in other regions a little bit away from the one you're trying to edit - that's basically why that kind of editing is not very productive.

Manipulating just one point without trying to constrain numerous other points does not have the same kind of issues, and neither does editing control points since control points act as more of a guide for how the curve is shaped rather than over constraining it.

- Michael