Points for having suggested translations accepted
I think it would make sense to award points to people (for that particular language tree of course) for having their suggested sentences accepted.
This might motivate (as far as they're motivated by points) people to do the right thing and actually log the error/omission that they feel is incorrect rather than complain ineffectively about about it in the Discussion for that question which you often see.
On other sites, such as the Stack Exchange sites, badges and/or points are often awarded when users do something the site owners want to encourage (like editing, adding a tag to a question, having a popular question, etc), and to the extent that an accepted improvement makes Duolingo even better than it is, then that should be encouraged with points, given that that's the 'currency' of the site.
This is a great idea! I'm going to bring this suggestion back to the rest of the team. We definitely do appreciate all the help that we get from the community. We are building this together (truly!). Thank you!