This is probably the way Paint.NET has implemented if clicking on Line/Curve and you are allowed to use a bend in several places.

I agree, part of the reason I used PDN is the line tool, and it would be nice if this line tool could curve as well.

Yeaa, And you could curve it as many times as you want in different places unlike Paint.NET where you could do it as much as you want but only in the allocated spots, this was a problem when you wanted yo do large curves

Good curve tool is essential. It would be valuable in digital inking and in any design-type work. If you want to make real difference with it, implement "simulate pressure" too (like in Photoshop or Gimp). Krita also uses curves to make selections, this could be very good idea also.

This is being worked on for this year's Google Summer of Code.

Pinta 1.6 was released March 1, 2015 that thas this feature implemented. See download page: http://pinta-project.com/releases

Really fantastic curve implementation! Very useful! Thank you!