Let's refrain from assuming anything about anyone's sincerity. As far as I can tell, most of the Windows 10 scaremongering on HN is nothing but FUD. The key logger argument is a case in point:
http://www.zdnet.com/article/does-windows-10-really-include-...
Yet, you unquestioningly repeat it.
Local system search while sharing some basic diagnostics data with Microsoft does not share the search queries.
WiFi passwords could be shared with your Windows 10 using Facebook friends, if you allow it. If you care about privacy that much, don't allow it, or better yet, don't use Facebook.
I couldn't find any evidence that Windows 10 shares any worthwhile application activity data.
Yet, it is somehow perceived as a Watergate-level of betrayal, but at the same time it is ok to praise Google for scanning your entire mailbox.
To me this just looks like a bunch of 90s kids struggling to shake off the "Evil Micro$oft" groupthink.