From John Gruber on Daring Fireball:
When you pin a link, you can refer back to it in the profile details for the contact(s) in that thread. That’s the popover you get by:
- Tapping the user avatar in the center of the top navigation bar on iOS.
- Clicking the “i”-in-circle Info button on MacOS.
Scroll down in that popover and there’s a section for pins, right above the section showing all photos in the conversation.
Gruber goes on with a few updates to the post to explain all the oddities with how the feature is currently implemented – the feature is a good idea in theory, though.