Improve comments

Author: ansd

deps/rabbit/src/mc_amqp.erl

@@ -474,8 +474,7 @@ convert_from_3_13_msg(#msg{header = H,
     amqp_annotations().
 protocol_state_message_annotations(MA, Anns) ->
     %% To efficiently overwrite MA with Anns, we first remove entries in MA
-    %% that will be re-added by Anns. We optimise for the common case where no
-    %% MA entries need to be removed.
+    %% that will be re-added by Anns.
     Fun = fun({{symbol, <<"x-exchange">>}, _}) ->
                   not maps:is_key(?ANN_EXCHANGE, Anns);
              ({{symbol, <<"x-routing-key">>}, _}) ->
@@ -491,6 +490,8 @@ protocol_state_message_annotations(MA, Anns) ->
           end,
     MA1 = case lists:all(Fun, MA) of
               true ->
+                  %% We optimise for the common case where no MA entries need to
+                  %% be removed: We avoid the list allocation in lists:filter/2.
                   MA;
               false ->
                   lists:filter(Fun, MA)