[cammil]

I think there is a theory that one "should" use the _other_ hand for any modifiers. Presumably and primarily so that the letter key is always pressed using the same finger and position of the hand.

[flyingfences]

> Presumably and primarily so that the letter key is always pressed using the same finger and position of the hand.

But it is. Hitting the left shift in the scenario described literally just takes pulling the left pinky down.

[floatboth]

I never cared about using the "correct" shift key.

[hfdgiutdryg]

I think it matters most for those with smaller hands. That said, if you were transcribing stuff all day long (i.e. typing way more than a programmer), you might notice less fatigue if you shifted "properly".