What I wanted to discuss is the fact that this OStatus endpoint was indended for account subscription, not for providing a way to interact with content, as Mastodon and other have started to do.
The user’s XRD document MAY have an additional link template with Rel equal to http://ostatus.org/schema/1.0/subscribe to indicate the endpoint to use for initiating a subscription on the user’s subscription server. The template should take a single argument, uri, for the account to subscribe to.