A lot of noise and little facts.
And it starts with the article in question.
Let me state forthright that I am a proud fan of Microsoft. I don't care that every time the register posts these juicy anti-Microsoft 'articles' the brainless masses reading the tripe jumps onto the comments section and merrily joins in in an effort to outshine each other in expressing their disapproval of all things Microsoft simply because everyone else is doing it. I choose to think for myself and will like or dislike something because I have hands on experience with it and not because I'm just forever regurgitating the same old nonsense everyone else is upholding as truth on the internet.
Here are the facts then. Windows RT was and still is Microsoft's vision for all things mobile. Windows Phone 8 as it exists on Nokia devices was an effort to gain a bigger foothold in the mobile industry. A rather successful one at that. It's an upgraded version of the Windows Phone OS that came before it. It is not Windows 8 or Windows RT regardless of the fact that is uses a tile interface. It's a different technology all together.
So why not put Windows RT on mobile phones straight away? Because it still needs a lot of optimizing before it will be able to run on the average mobile phone. Tablets and PC's are more powerful and able to run Windows RT.
I honestly do not get people's dislike for Windows 8 as its fast, stable and I am yet to find a game or program that cant run on it. It uses the Windows RT interface but even on a PC it's something you'll end up loving once you figured it out. But then I'm not afraid of change and I'm always upgrading my hardware.
I grew up with Microsoft products and I'll probably grow old with them too. Sometimes they miss the mark and sometimes they get it right. Then again, so does all the other players. I've read countless complaints about Android and IOS not so long ago. Linux distributions are hit and miss although more in bundled apps and ease of use than architecture. Nobody gets it right all the time.
One last thought. It seems the main complaint regarding Windows Mobile / RT is the limited functionality. And sadly this is indeed an issue. It's the same issue that Android has. There's not enough people creating apps for the app stores. Which is why I still cling to my iPad as my go to tablet of choice. I suspect though that developing and maintaining Windows RT / Windows 8 apps will be far more easier than on other architectures. And perhaps therein lies my main reason for sticking with Microsoft. Through it all they've always made it easy to develop software for their OS.