"This comment is pinned to a missing element". This phrase means the page has changed, and the pinned comment’s original web element no longer exists on the page.
"This comment is pinned to a hidden element". This means when a webpage contains dynamic elements like drop downs or modals, a pin can be placed to mark a specific location. Although the pin will be positioned correctly on the page, it may not reflect the exact state in which it was placed. But don't worry - automatic screenshots capture the precise location when the pin was placed, providing visual context. To identify pins attached to hidden elements, simply click on a pin and you'll see a message stating "This comment is pinned to a hidden element." Additionally, a small grey circle will appear on any pin on the canvas that is attached to a hidden element.