I wrote a fun solution one time where the document comes with a token that needs to mature for a duration depending on the user. Then, when your [say] 30 seconds are expired the input area is displayed but the submit button only appears if you input enough characters - where enough again depends on the user. If you are likely to make low effort postings I want at least 500 or 1000 characters worth of low effort. In even worse cases ill also hold the comment for moderation - until I get to it. (which might be a long time)