Call attention to the Public Inbox Delivery section in Public Addressing.

It may be that these sections should be merged?

index.html

@@ -929,6 +929,10 @@
           users, without authentication.
           Implementations MUST NOT deliver to the "public" special collection;
           it is not capable of receiving actual activities.
+          However, actor has a
+          <a href="#publicInbox"><code>publicInbox</code></a>
+          endpoint is available for efficient shared delivery of public posts;
+          see <a href="#public-inbox-delivery"></a>.
         </p>
       </section>
     </section>