Martin, How about storing the last e-mail/note sent by session and checking to see if the contents of any new e-mail/note being sent match the contents of the last one sent by that session exactly. If it does, present the agent with a verification link "Are you sure you want to send this again? Yes/No".

...

I'm sure this must happen to other people. I find myself pressing "reload" in my browser after submitting a response to a ticket and see that my original response has now been sent twice. Any ideas on a way to prevent this from happening within OTRS itself? Perhaps warn if the new reply matches the one just sent?

Normally this is done by the browser (popup - post form again ...).

Anyway, if there is a good idea to do this by the webapplication let us discuss this.

Thanks, Paul