[Bitman]

a lefty would have the analogous disadvantage confronted by a righty

I disagree. For the lefty,being confronted by a rightly would be normal. The lefty would also have a disadvantage when confronting a lefty.

[SunkenCiv]

For the lefty, the first time confronting a righty in combat would leave the lefty with the same disadvantage as the righty has.