comment around why we do this, make check more explicit

lib/msf/core/exploit/tcp.rb

@@ -194,9 +194,13 @@ module Exploit::Remote::Tcp
     super
     disconnect
   end
-  
+
   def print_prefix
-    if rhost && rhost.split(' ').length < 2
+    # Only inject a host/port prefix if we have exactly one entry.
+    # Otherwise we are logging in the global context where rhost can be any
+    # size (being an alias for rhosts), which is not very useful to insert into
+    # a single log line.
+    if rhost && rhost.split(' ').length == 1
       super + peer + ' - '
     else
       super