Addendum to my previous post - I've been able to replicate the behavior mentioned about the time stamps being out of order.
Essentially, on the first page all timestamps are totally fine. It's when you hit the "More" button on the bottom of the feed when things get a little crazy.
Our engineering team is focusing on fixing the settings and Subscriptions Only issues in the immediate term but this issue is in investigation.
For the time being, if you're interested in checking out the Activity Stream, I'd recommend using the version on the All New Posts page
. From here, you have all the same functionality with twice as much of the content on the home page version of the stream. Otherwise, the Classic All New Posts page is a great resource.
I'll keep you posted when I know more. Thanks again for your patience.