What is so special about this box?

Gyazo
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As you can see, there are 4 boxes and one separate one. They are all named the same. What is the reason for this chosen, separate box? I am eager to open it.
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We're testing a new feature that gives the option to view discussion comments in chronological order. Some testers have pointed out situations in which they feel a linear view could be helpful, so we'd like see how you guys make use of it.

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