Good job on moving the thread!
You can edit individual messages in a thread similarly. This gets darn useful when someone goes off and you want to just delete the post, not the whole thread.
When you're looking through a thread, you'll see the same sort of check boxes on the right of each post.
Click on the check box of a post you wish to do something with.
Now look down at the very bottom left corner of the browser window. You'll see Quick Reply, Reply, and Post Tools.
Click Post Tools, and a pop-up of actions you can take will appear. Usually you'll use Delete Posts.
One more pop-up to say why you're doing what you're doing, and you're done with the edit of the post.
If you want to try it, in the Stranded and Frustrated thread, I posted a beer clinking emoji at the end. Go ahead and delete that post of mine. Do say it's for practice or such.