A GM can use this basic form of a link to a specific message:
<a href="URL for game here#msg. no. here">Text for Link here</a>
Just as a "real-world" example:
<a href="https://www.rpol.net/display.cgi?gi=9590&ti=1946&date=1558952461#1"Link to Post No. 1 in this thread"</a>
This yields:
<a href="https://www.rpol.net/display.cgi?gi=9590&ti=1946&date=1558952461#1"Link to Post No. 1 in this thread"</a>
(since I'm not a GM here...)
Non-GMs may also just paste the URL to the message. Go to the forum where the message is that you wish to link to, copy it's URL from your browser window, paste it into your message where you want the link displayed, adding the #msg. no at the end.
https://www.rpol.net/display.cgi?gi=9590&ti=1946&date=1558952461#1
yields:
link to a message in this forum
This message was last edited by the user at 16:01, Mon 27 May 2019.