By the way, thanks all for contributing to this thread. In case it didn't become clear, I was collecting information and material for the Common Misconceptions chapter of the BattleMech Manual.
You can also add this one: a target movement modifier is always based on the
total number of hexes the 'Mech moved.
While it's usually correct, there is an exception: the 'Mech declared walking movement, moved backwards to some point and then moved forward. In this case only the hexes the 'Mech moved forward are counted when determining the target movement modifier.
That's a subtle moment, I think, I am not the only person who had such misconception for some time.