Found in production too.
{F3975611}
The screenshot is an illustration of the following scenario:
1. On any Flow board click to Thank some users in one post - all clicked 'thanks' will change to 'thanked'.
2. In the same post click on any Reply and after typing in the post, save the post.
3. All previously displayed 'thanked'' will changed to 'thank'.
If a user notices it and clicks again on the same 'Thank', the 'Thank' changes to 'Thanked' and no duplicate notifications are sent.
More severe is the following scenario:
After #3, a user sees that **all previous** 'thanked' labels in the same post done by other users are also changed to 'thank'. If he clicks on any of them, then a new notification will be sent which will be a duplicate to a thank notification received much earlier.