I did, but none of that is mentioned in either the original Mozilla blog post or this article. We have no reason to believe that disabling desktop mode preclude

I did, but none of that is mentioned in either the original Mozilla blog post or this article. We have no reason to believe that disabling desktop mode precludes an application acting as a Gecko rendering bridge for a Metro UI. They seem completely unrelated: in fact, the only way they could be is if one expects a Desktop Firefox to run in the background and serve pages to Metro. That's not listed in their design plans and, furthermore, is not how IE works on the same platform. I will admit to not having read the Application development guidelines for Windows RT. It could potentially be a sandbox violation, depending on the aforementioned guidelines - however, that's a completely different issue, and it's not "Microsoft locking Mozilla out of the market by removing desktop mode."