Optical compensations and writing tools

Hello all,

While reading this thread one the use of the term 'stroke' in typedesign, I noticed that Frode commented:

"I would absolutely a thread on the various “optical” compensations & their relationship with traditional writing tools, such as the notion horisontalz thinner than verticals look the same."

Since I am in the process of writing a thesis on a related topic, and I wholeheartedly agree with Frode, I thought I'd start such a thread here. I hope my inevitable bias will not clutter the conversation.

To start the discussion, let me ask:
1. How do writing tools, or the heritage thereof, influence our perception of letter shapes, and thus the optical compensations employed by typedesigners?
2. To what extend can we find evidence for the influence of writing tools on optical compensations in different scripts?

A non-exhaustive list of (debatable) examples:
a. Horizontals that are thinner than verticals look the same
b. Strokes in south-eastern direction that are thicker than strokes in north-eastern direction look the same (to me, at least)
c. Does b also apply to the corresponding directions of parts of a circle/curve?

Please do add questions and examples!