I think it would be an excellent idea to allow readers the option of suggesting improvements/changes to sentences/paragraphs in a chapter in some way. Of course, this system would have to have a way of blacklisting certain users from leaving suggestions if they leave malicious ones.
In this system, the original author would have to click on the suggested fix to implement it, and this would perhaps also give the account that suggested the change some "Suggestion Points," which could indicate that they are good at leaving suggestions.
Hope this suggestion would be implemented as it would greatly increase the professionalism of certain stories and the ease of editing out any mistakes in the chapters.