Weight Painting - Stiff vs Flexible Deformation I have a rigged and weighted letter A. I particularly need to understand why, despite a nice gradient in the weight painting, a part of the deformation is nice and flexible (marked in green on the screenshot). And part is stiff like it's 100% weighted, though it looks like a gradient in the weight painting (marked red in the screenshot). 

What I would like is that when I pose the bone, the deformation follows the weight-painting gradients on both sides. So it's flexible and smooth. 

I would like to understand how to control this, so I'm more in control of the deformations.

I'm attaching a stripped down version of the .blend file.
What you're missing is another bone for the last horizontal part of the mesh, which will act as a "balance". In Blender Weights are always normalized, to distribute the movements between deforming bones, but if a vertex is weighted to one bone only, the normalization is calculated between a weight and zero: so a weight of 0.0001 and a weight of full 1.0 are treated the same way (both values are infinitely larger than zero).

The vertices in your "green zone" are affected by two bones, which blend their action, while the vertices in the "red zone" are affected by one bone only, leading to a "rigid" behaviour.