>On my system, replies in the Python forum are appearing twice (see attached images). These are the same messages being displayed twice (i.e. same message ID), not two different messages.
>
>As a test I made a reply, after hitting the global refresh message#1568956 appears twice in the second image.

Only once instance of those messages is in fact in the database. I am not sure however if this is related to what Naomi says. Are you always seeing that when you show the map of that thread? If yes, are you able to clear the temporary files, restart browser and see if the same happens?