That could be useful in all sorts of comments. A music composition app that destroys any work that's too derivative. A Twitter client that blocks repetitive tweets. Maybe Hacker News comments could benefit.
A hacker news bot that auto-posts common messages would save us lots of arguing time. e.g. Whenever a submission references some c/c++ code, the bot could auto-post a whole thread of arguments about 'why are people still using this insecure language?', thus saving HN denizens from posting and arguing over the same thing...
The path to innovation shouldn't need rails. Maybe what I'm trying looks pretty similar to things that have come before, but perhaps it's different in some way I understand and which a machine does not. Rather than a destructive feedback mechanism which would only discourage brainstorming, I'd rather see some kind of "genericity meter" to provide real-time feedback without stopping the artist from going down a path that is at least new to them.