If I create a team site and add a site feed to it, it works. It shows the title: Newsfeed, and input box and the line that says "It's pretty quiet here. Invite more people to the site."
When I create a blank site and add a site feed to it, it shows the title and the line of text without an input box.
I'm wondering why that is. I've invited myself, confirmed that the site is shared with me, but still no ability to post probably pictures of my cat or thoughts I just had that no one cares about.