…after you re-open the modal or select another emoji.
Reason:
Even the most used emoji would be knocked off the list after a while, if you use any emoji outside the recent. Consider the sequence:
✅, 😃, ✅ (from recent), 😀, ✅ (from recent), 😛, ✅ (from recent), 😎, ✅ (from recent), and so on
With the previous logic, the check mark emoji would leave the list, even though it used constantly and (and the time of removal) would the the second most recent used emoji.
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It doesn't update the list when you use the recent list so that you can click an emoji repeatedly and it doesn't shift from under your mouse cursor.