TL;DR: a small team at Microsoft (modern.ie) have a site old-ie compatibility scanner that they've written in node and want to integrate into a CMS. This probably isn't a larger strategy or play at Microsoft. It might be a sign of internal change among developers there, which might change their business strategy at some point in the future, but they're definitely don't seem to be "throwing their weight around" just yet.

They already have far larger investments in plenty of other CMSes:

* Sharepoint (the goose that lays the golden eggs),

* Umbraco (which IIRC runs asp.net, iis.net, windowsazure.com, and possibly [parts of] technet and msdn),

* Orchard (which is theirs, albeit through the OuterCurve foundation, which is one of MS' OSS outreaches),

* MCMS (which is horribly old & expensive, but still out there and in use),

* A bunch of internal CMSes, and other stuff that they developed themselves to tie in with backend systems (eg CRM)

Hell, they did more with Oxite before abandoning that than they're planning with Ghost.

Maybe MS as a company want to get more into node, but that doesn't really seem in line with their larger strategy (even though they definitely are starting to embrace OSS more, particularly on the web teams) - so it's probably just likely that one team wanted somewhere that they could test out the library they've written.