Patrick, try the following:
1. Go to your library
2. Right-mouse-click on the text link of your video file (e.g. "Kid on Roller blades...") then select "Copy Shortcut"
3. Start a new post and click on the text box under the "Link (enter a URL if you...)"
4. Right-mouse-click and select Paste.
5. Post the reply as usual.
And, here it is to test...