The github native viewer doesn't seem to allow for setting color to countries - or at least I can't work out how. You'd need to host it outside of github with json to do it, I think, which puts it on par with the current map?
My team works like this with a twist. You merge your own pull request. You have developers, designers, pm's, etc to help review the change. You use them if you need them and you take responsibility for your bugs. We'll drop everything to review someone else's pull, and in turn that happens for your own pulls.
We also merge our own pull requests but there is less concept of code ownership. Bugs can be fixed by anyone who grabs them and assigns them to themselves. Blame may point out the cause and you can send the author a friendly message on Skype so they are aware of your fix. Perhaps they can even mark your fix as peer reviewed while they're at it.
I'm not quite sure what you're getting at but it's weird to me too. You never know what lead to that decision (target markets, promotional video production issues, or maybe they just wanted to play off the "girl at home on the phone with friends" archetype) but it is odd.
The author glosses over the fact that encoding of special characters in the hash is broken in firefox. As an application there's no way to know if you're getting the data you want or url encoded data. Base64 encoding (with replacing chars like $ which most im and email clients fail to autodetect as being part of the url) seems to be the only bet at the moment. Putting the data in the get request and ignoring it on the server also seems to work well.
When node switched to libuv it didn't degrade io performance on unix hosts; io in threads has been competitive with evented io. I don't think async io was even considered, but let me know if you dig up anything.