#672: docs: more cleanup and fixes

src/active-messenger.md

@@ -2,10 +2,11 @@
 \page active-messenger Active Messenger
 \brief Asynchronous send/receive of messages
 
-The active messenger, accessed via `vt::theMsg()`, asynchronously sends and
-receives messages across nodes using MPI internally. When sending a message, it
-uses the \vt registry to consistently dispatch messages and data to handlers
-(function pointers, functors, or methods) across nodes.
+The active messenger `vt::messaging::ActiveMessenger`, accessed via
+`vt::theMsg()`, asynchronously sends and receives messages across nodes using
+MPI internally. When sending a message, it uses the \vt registry to consistently
+dispatch messages and data to handlers (function pointers, functors, or methods)
+across nodes.
 
 Each message contains an envelope `vt::Envelope` to store meta-data associated
 with the message, such as the destination and handler to trigger when it
@@ -16,8 +17,6 @@ destination node. On the receive side, the active messenger is always probing
 for a incoming message and begins a transfer when it discovers one. The \vt
 scheduler polls the active messenger to make progress on any incoming messages.
 
-\copydoc vt::messaging::ActiveMessenger
-
 \section am-simple-example Sending a message
 
 \code{.cpp}