It's kinda back and fourth, any arguments you can make either pro or con can work for and against it. For instance smart people would usually leave their ideas open for opinions and interpritation, at the same time you could have some trolls or stalkers constantly hounding you. Having that option to close your own thread keeps them from derailing your original point, or allows you to end it if you feel the discussion has come to a close or strayed from the original point.