There is no pinning in that sense for users but there are two other tools that you can use for your favorite topics:
- Use the Tracking button on the bottom of the page and set which type of staying up with the topic activity you want:
The same button is available under the slider in the sidebar:
Clicking on that button will bring you options to choose:
- Use the Bookmark option for the first post in the topic.
This way you can build your collection of topics or posts which are accessible when you click on your avatar in the header, just under it or if you use link Bookmarks on the top of the page.