First of all, while you can post comments on sites of at least 50 words, you will not get paid for them unless they are at least 100 words. This change was actually made a while back, but I just haven't gotten around to writing about it until now. This is pretty easy to reach and ensures that people are giving enough detail and that they have actually used the site they're writing about. My tip: write detailed comments, then copy and paste into MS Word to make sure you have written enough.
Another update is that now you cannot cash out unless at least 25% of your earnings are from writing comments. This should not be a problem for anyone using the site legitimately. It's just a way to make sure that people are actually contributing instead of just randomly grading sites they haven't used.
Finally, owners of the sites being reviewed now have the option to write "rebuttals" to user comments. Unless you're a site owner, this won't really affect you at all. Basically, it just allows them the chance to state their side of the story.