Its interesting that simply restricting immediate commenting might at least deter useless comments. People who are commenting in order to elicit a response, i suppose, probably have less important things to say. Or maybe they wouldn't say them if they are not granted the immediate satisfaction.

I assume it would kill some collaboration/innovation like on HN or a meaningful subreddit, but maybe no one really ever has anything meaningful to say when reacting to general news...

I guess it would also produce duplication from many people not knowing something was said already (however, the duplicate reactions could be monetized later down the line maybe...)