It one of the recent topics, I wanted to link to this topic, remembering that it is pinned. And it is pinned, indeed, but only in the "meta" category: when I choose "all categories", it is not shown as pinned. Is this the normal behaviour of Discourse?
For me it disappeared once I had marked it as read. It is still on the front page if I open an incognito tab.
Reviving this topic, since it looks like the behavior is consistent: whenever I open the linked topic, it switches from "pinned globally" to "unpinned", unless I set it as "pinned globally" manually. I'm not sure, is this a feature of Discourse or something unexpected?
User -> Preferences -> Interface
Automatically unpin topics when I reach the bottom.