I have been on forums for 20+ years and have never seen this before? What is the purpose other than “wasting site resources” 
Is this the Discourse requirement for 20(?) characters in a reply?
If so, the Discourse designers wanted to encourage “conversations” and discourage relatively meaningless “me too” or “I agree” posting chains 
It can be irritating when you want to ask a simple question in reply
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I agree. …
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Me too, …
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<20 characters apart> 
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Gave me a good chuckle. And that’s hard to do.