Why do I see the "Mark as solved" button?

Question

Toaster

Hello everyone
I'm going to a random question. I read it. I scroll down and look - under the answers I have a button "Mark as solved", I clicked it purely for fun and really! I marked the answer as a solution on someone else's question))
PS: most likely it's just a banned button, because next to the question it does not show that there is a solution, but if you enter, the button turned into "Marked as a solution"

Answer 1

Congratulations, you have discovered the system of collective decision making