Hey Carl,
if you click on this “Dec 20” on the posting you mean, in a little popup, you are offered the direct URL to the specific posting. The button besides it then copies it to your clipboard. This way you can insert a link to the specific posting in your own post: By using the little symbol that looks like two chain links, that you see in your message cmpositor window in the upper row, and where you can paste the address from the clipboard.
E.g. like this: