I'm perhaps annoyed because of contextual reasons rather than anything else. If you want to ignore the facts of how things are defined, then be my guest and while it's irritating that someone won't listen to reason I can't do my best. But I spend an inordinate amount of time listening to you accuse me of being brainwashed/ anti-British etc. In the latter case you did at least apologise once I'd pointed out your error (I'm thinking of the Corbyn anthem thread, by the way) -- in the former, I still think you believe that. And yet you never seem to bother yourself with troubling to do any research any more. Here, some cursory research would show you that you have been simply wrong about basic facts -- wrong about CGP Grey, wrong about your use of definitions -- when it took me not 30 seconds to find the video of CGP rubbishing the US system, and not much longer (albeit in the past) to do some equally basic research into the differences between various voting systems. And you call me brainwashed?! You can't even be bothered to check if you're right or not, instead choosing to basically parrot the sort of nonsense FPTP fanatics come out with every time someone suggests that there might be a better way (Cameron, sadly, is another example of this, which means that for now the debate doesn't matter anyway as the people in power won't listen).
That is what is irritating -- not just lack of knowledge, but the lack of any desire to, you know, try and learn something for a change.
If "PR at seat-level" is the best you can come up with, you should know that this is a contradiction in terms. Since only one person can win a single seat, it follows automatically that single-seat representation can never by proportional. Only multiple-seat systems -- ie, systems such as the one currently used for EU elections, where each constituency contains somewhere between 7 and 10 seats -- can hope to be at all proportional. "PR at seat level" is as nonsensical a statement as, say, chocolate with no cocoa beans, or conservative socialism. They cannot -- they do not -- go together. AV is not PR in any way whatsoever.