Earlier quoted context omitted.
Microsoft has joined Open Invention Network a while ago and AFAIK (though I can be wrong) Valve is also member of OIN. They can't really attack anyone using their patents now. And Valve is not exactly a small startup that's possible to sue into debt. Even though they're much smaller by headcount they certainly do have money and desire to fight any kind of legal battles. And with amount of goodwill Valve has from it's…
It is as easy as having Windows and XBox APIs that Proton isn't able to easily replicate, while requiring them for Windows Store and XBox Game Pass. Valve got lucky with UWP. No need for patents. Also there is the whole question Microsoft has outlived its founders, will Valve be able to do the same, and those that come after Gabe will they sell it, what would their view be regarding Proton, and so on.
This will do more damage to Microsoft's position rather than Valve. They already lost current generation of console war and weakening their positions further by breaking compatability would't do them any good. Also Apple eating into their laptop market share by ARM offerings and have it's own compatability layers for graphical APIs.
Microsoft cant do much of anti-competetive vendor lock-in by technical means now. It was possible for them to stop something like Open Source community efforts, but likes of Valve and Apple are so much more resourceful. Everything they do on Windows can and will be reverse engineered.
> Also there is the whole question Microsoft has outlived its founders, will Valve be able to do the same, and those that come after Gabe will they sell it, what would their view be regarding Proton, and so on.
Here I'd tend to agree. There is a huge questions whatever Valve-after-Gabe can continue as it's now.