To link to a particular thread (or at least a particular page of a particular thread) just copy the URL in the web-browser.
Here's how to get the URL for a particular post. This pic shows a particular post outlined in red:
Notice at the BOTTOM of the post, there is a link, circled in green, that says "Link to post". Right click on it, then "copy link location". This will copy the URL into the computer's copy/paste buffer. Then you can create your new thread and control-v (or paste) and paste the URL into your new post, thereby providing a reference the post desired.
Instead of right clicking, you could actually select the link (left click), which will update the web-browser to point at the specific post. Then you could simply copy the URL from the web-browser window.
your friend in noticing different ways of doing things between boards, arthur