I created a thread in Chart Support and everything created just fine. Later I received a reply asking for more information so I went back to the thread and wrote an update. When I verified reCAPTCHA and submitted the thread page reloaded, but gave me no message or indication my post was received. I even waited a while for an email indicating my post was received or is being moderated. Having never received one I went back to thread (still not seeing my reply) and wrote another because I thought it failed. Upon resubmitting new reply I noticed same behavior, but this time I had my reply text copied so I could re-paste it and submit it again. This is when I finally received the “this is a duplicate reply error message”.
My suggestion: If you are moderating post replies please place a notice message post submit so the user knows the post was received and is pending moderation. This way the submitter at least knows what happened and doesn’t wander around in the void.