It's an anti-samefag/troll tool that Futaba and other Japanese boards have, and it has been requested here going back to at least the StrawberryHeaven days

Since we've had issues for a while now where 1-2 users will repeatedly post the same thing over and over and derail many threads (making Heyuri feel stale and uncreative to those who are unaware that 99% of it is just 1-2 users), it's an apt addition!