There is a question that has been posted that had the same issue but the resolution did not work entirely for me.
In my situation I am using a comments field that I want appended. I have all the settings for that set up correctly. I have a workflow that checks different statuses of my document and will send out emails to users based on certain status, etc.
At first, the comments field would be saving 11 - 14 times per save. I then updated my workflow to have the very first stage update the field with a blank string. That is the information that I have seen to fix the duplication problem for other users. By doing that I reduced the duplication to 1 extra copy.
How do I get rid of this last duplicate? The very first thing my workflow is doing is clearing out the field. I have also verified that the duplication is happening sometime before my first action in my first stage of the workflow by putting in a 2 minute wait at the very beginning. So sometime between when I save the item and it actually starts running the steps of my workflow it is adding this duplicate.