I was more impressed that it lasted an entire 24 hours. They're exposing it to the festering cesspool of Twitter, and it holds out for an entire day? That speaks to the quality of their anti-abuse measures more than anything else.
If you use Livestreamer and an IRC client, you can run Twitch streams outside your browser. That's what I've been doing - I haven't had flash installed since that cross-platform RCE bug late last year.
I'm pretty sure that example is actually fine - if there's a concurrent writer, the modified value will be loaded into oldValue. Repeating shared.load is unnecessary since that operation occurs as part of compare_exchange_weak.