@nprofile1q... - Interesting. For some kinds of math questions there's a right answer, e.g. true-or-false questions (which can be very powerful in mathematics). For these it can be really helpful for beginners to know what's the right answer. For other questions, more open-ended, there's nothing at all like a unique right answer.
I personally never even paid much attention to this check mark business.
Personally I think the competitiveness comes in when we see charts like this:
https://mathoverflow.net/users/2893/john-c-baezI'm the 100th best person on MathOverflow this month, etc.