bezier curve with bevel object: nice corner A bezier curve with a bevel object and a bend with a free vertex.
How is the bend made nice with a continious width?
The increase of resolution (Data > Geometry > Bevel > Resolution) smoothes the bends of 2D curves, no effect on 3D curves.


Thank you for any hint!
As Duarte Farrajota Ramos commented, it isn't possible as a 3D-curve at the moment.
However, you can use seperate 2D-curves (see the links in the comments) or make at least the left joint of the corner horizontal:

Use shrink/fatten (alt+S) to fatten it by the factor $\sqrt{2}\approx1.41421$