MS no longer owns a blogging platform AFAIK. It used to be Microsoft Spaces, but they converted people to something else last year when they shut that down. I moved my blog to Wordpress, but I don't recall if there were other options to port the content to a different service (and I don't blog often enough to give you any sort of feedback on WP). So that may be the closest thing you get to a "most favored" blogging platform.

Bing has had a "social search" feature for a while now. http://social.discoverbing.com/


Note: I'm a Microsoft employee, but do not work on the Bing team.