improved control about Display Smoothing

I find the default display-smoothing could be tuned up.
Even at SD-Level 3 I still get a Diamond-shaped Highlight - so I tend to subdivide to higher levels than actually necessary. Maybe Smoothing-Angle controls should get exposed to the User?

You may have got this option checked, Edit > Preference > General > Subdivision smoothing same as base mesh.

No, I have this unchecked.
But scratch that request - I just tested in two other applications and they also only start showing a proper Highlight from SubD-Level 5 on upwards (on a simple Cube with 6 Faces).

well dont really see it as a issue since your not going to subdivided a cube with no extra edges in most cases.

if you wanted a beveled cube look add in support loops, and bam there is enough geometry to get good highlights on the edges at olny subd level 2 or 3.