Technically, there was at least 1 free seat since the woman wasn't using it anymore.
But that begs the question, assuming the entire plane was full then the lady was sitting next to at least one other person. They moved her from that seat to be in next to the couple in question. So it seems to me there is no situation where it's not extremely messed up.
As many have said, it shouldn't matter.
Personally, I have been known to look at email addresses because I assess everything the resume gives me. No, I don't really care what provider you choose, but it's a tiny bit of information.
So if your email name is "BigBootyQT" then I have a glimpse of your personality and how you may or may not fit in the role. That's a real example BTW. It also might bear light in other ways, say if you're applying for a job in cybersscurity but you're using a yahoo email. Yeah, that's a negative mark.
Will any of this be THE reason I ditch somebody? No. But it weighs with the rest of it. I would not disqualify somebody for a typo for instance, but it is a negative because that should not have occurred (especially of the role requires attention to detail).