There are some direct ways to express agreement in Chinese, like 對 or 好. At the same time, the negative statements described are not unique to Chinese at all. It's not that deep, really.
replies(1):
不错 is literally "not bad", but it's more positive than the American English equivalent, being basically semantically equal to 很好 (lit. "very good", although in practice just plain old good/OK). You can even say seemingly absurd things like 很不错 "very not bad" (= excellent); or you can tamp it down with 还不错 "also not bad".
Funnily enough, in British English, "not bad" is high praise; but you still wouldn't say "very not bad".