You can remove the "censorship" with a 30-second config change. I don't understand why the people on that forum are so up in arms about something this trivial.
I'm not sure how much of a priority you think this is, but the one main problem I have with SageMathCloud is the lack of good documentation. Mathematica, as a counterexample, has comprehensive, searchable and easily accessible (just hit F1) docs. I humbly submit that including a way to browse and search documentation - not just Sage-specific, but also for every library it includes - would go a long way towards making SMC more usable.
It's a check - as of Android 5.0, Google's OTA updater scripts refuse to overwrite your /system partition if its checksum isn't on the known-good list. Rooting inevitably involves writing files to it, so OTA updates will stop working with an uninformative "Error!" in recovery. Whoever came up with the idea should be fired, but that's Google for you.
See [1] for details from the author of NRT [2], which can update your phone from factory images without wiping it. The procedure is a bit more involved if you're not on Windows - IIRC, you have to download the correct archive from [3] and modify the update script so it doesn't try to flash userdata.
You might be interested in su3su2u1's teardowns of HPMOR [1] or at least his review of the finished story [2]. The main takeaway is that MOR!Harry does not, in fact, employ any "Methods of Rationality", usually leaping to "obvious" conclusions without any experimental evidence whatsoever. The author then opts to make the fictional universe fit these conclusions instead of the other way around. Not only that, but most of the science/rationality references are either wrong, incomplete or not applicable to the situation. So despite having entertained me most of the time, HPMOR is not what I would call a praiseworthy piece of writing.
Miracast isn't "open" - devices require certification, and the Miracast and Wi-Fi Direct specifications cost $200 each. It's also supported by relatively few devices right now (since, you know, certification), and I seem to recall there are some compatibility issues between manufacturer implementations.