In this thread, I learnt that it’s possible to unpin posts that have been pinned by the moderators:
This goes along with the earlier lesson that it’s possible to mute particular forums that I never go to.
I would just like to thank @codinghorror for these two features, which means I can customise the displays and make it easier to focus on things I’m interested in, and to ignore stuff that I don’t want to see. Nice Discourse features!
In six months, after the formerly pinned thread has sunk to its rightful place near the bottom of the thread listing and you’ve half-forgotten what it says, how do you find it again?
Use the in:pinned search option.
Search results for 'in:pinned' - Straight Dope Message Board should bring up all the pinned threads on the whole board. You can narrow that by searching in one particular forum.
Fascinating. Thanks.
That wasn’t meant as a brush-off. Now I also know how to get the unpinned stuff if I need it. I’m just keeping the intro for each forum, with the lists of mods. If I need to check the rules for something, I can use your tip to find them.
I like this customization ability.
Wasn’t taken as one. 
I bash Discourse, but I do so like the way it handles pinned posts.