For future reference, here's how you do it:

1. Go to the post in question.
2. Mouse over to the post number in the upper right corner.
3. The mouse pointer should change to a hand.
4. Right click on it.
5. On the menu that appears, select "Copy Shortcut". This will put the url in the clipboard.

Once you have the url copied, you compose your message and do the paste/control-v trick, and you're good to go.

This is why I said it was a lot of work - you have to go to each reference.

I don't know where I found that out - it was a long time ago.

And now you know.