Speaker popularity

Speaker *Polarity* (sorry autocorrect)
                      >:( 

This is sort of a poll question for anyone to chime in. In general, I believe people on this forum have a good ear for finer details.

Can you tell the difference if the polarity of *both* speakers are reversed?

I remember a thread from way back where someone shared an experience of a vendor at an audio convention that deliberately reversed the speaker input connection?

...Yes, no, depends(please clarify).

If yes, how would you describe the difference.
Thanks in advance:-)