Board Thread:Questions and Answers/@comment-70.29.78.196-20141206033936/@comment-16810903-20141206120315

It's not necessary it will appear in puzzles only, but per the developers, this symbol that you see on the leaderboard is part of a new game feature that they are testing out. It was not their intention to publish it today as the feature is not yet complete, but they’ll give us more information about it soon.