Thanks Harry!Two easy ways to see if you replied to a thread. First is to scroll to the bottom of the page. It lists both "Who read" and "Who replied".
Second way is to do a search. Click in the Search box which opens the Search dialog. In the "By" field, type your user ID (handle). Then select "This Thread" in the box that defaults to "Everywhere". That will bring up a page with links to all of your replies to the thread.