At the upper right of each message is an indicator of how long ago it was posted (or the date, it if it’s more than about a month ago). Click on that and a window will appear on your screen with the URL of that particular post in it. In that, just click the blue button to the right of the URL:
This copies the link to your computer’s (phone’s, etc.) clipboard, so you can now close the little window. Go and type your reply, where you can now paste (⌘V on a Mac, Ctrl+V on Windows, or whatever way your phone or tablet uses) the URL, which will look like this:
https://forums.kitmaker.net/t/chrysler-tv-8/47891/153
But once posted (and in the preview), it will look like this:
People can then click on the title to go to the message.
If you want an inline link, do it like this:
I explained it thus in a somewhat protracted backstory over within [my parallel thread “Chrysler TV-8”](https://forums.kitmaker.net/t/chrysler-tv-8/47891/153).
That is, put square brackets around the text you want to be clickable, and then put the URL in round brackets immediately after that, with no spaces in between.
This will look like:
I explained it thus in a somewhat protracted backstory over within my parallel thread “Chrysler TV-8”.