ISSUE SUMMARY:
I started writing a discussion, but I left the form open a long time. I was still logged in, but when I clicked 'create discussion' I saw 'invalid token' (which I know is a Joomla problem).

I went 'back' on my browser and on the discussion page clicked 'create discussion' again. The button didn't appear to work, so I clicked it several times.

Then the email notification message was sent 3 times.

Is there a way of stopping the same discussion being emailed several times in this situation?

Hi, Susan.

From your description I understand that your Joomla! session just expired. After that you tried to perform registered user restricted action so you get "invalid token" notification. Code was executed anyway and if you clicked few times - you executed it the same amount times.

Hi Michal

So if the user clicks a few times is there a way of stopping the action happening several times (i.e. stop discussion being created 3 times)? ie if button is clicked once it is disabled so you can't click it several times?

HI, Susan.

It happens only in that specific situation when session is timed out and you trying to send something - result page can't be loaded (as it usually is after action is done successfully). This is session error... something like clicking few times on application icon in Windows when system didn't finished to execute previous click (what results with few program windows opened one after another).