I think, we need contribution rank as we have rating rank. I suggest we follow rhythm game model.

For example

• SS: > 100 contribution
• S: <= 100 contribution
• A: <= 50 contribution
• B: <= 30 contribution
• C: <= 10 contribution
• D: <= 0 contribution

We can make the system more generous by following plus and minuses:

• B+: <= 35 contribution
• B: <= 30 contribution
• B-: <= 25 contribution

This will incentivize peopel to make smarter posts also rhythm games are brilliant: 初音ミクが大好きだ