I had Sierra installed as a Beta, and also installed the GM version of Sierra when it was available. Oddly, while Mac OS Sierra showed in my purchase list before it became available to everyone, it doesn't show any more. According to the MAS, I've never "bought" Sierra. I posted a bit ago asking others if that was their experience too; and, everyone said "yes". Here's why, I think, Sierra is different. By making the App a "downloadable" app vs. a "Free" app, Apple no longer requires an active MAS account to download the latest MacOS. Also, by disallowing "purchases" of MacOS Sierra, re-installing Sierra on a computer that you're selling (for example), no longer requires proving you've purchased a free upgrade. Also, by having Sierra as a downloadable (vs buy for free) app, there's no ability to leave a rating and/or reviews. Apple, I believe, wants Sierra to be downloaded by anyone/everyone, and for those people who are clueless and just like to bitch in feedback areas, there's no place to do so. Seems like an interesting approach to Mac updates. It's really making the upgrade much closer to a update by dropping the bar to acquire the latest version of MacOS.