Wrong. Your answer is a straw-man. The newbie did not ask what a decentralized currency was nor how it works. He only asked 'is Bitcoin one'; that's a yes and no question that can be expanded, albeit it would be redundant in this case. Imposing a character limit will not reduce any sort of spam but would rather negatively effect users that contribute by excluding their constructive albeit short posts. Spammers would just re-write more of what others posted to get above the limit (pretty simple actually).