But they do have a time limit on leaving a review, as far as I can tell.
You can do an additional remarks later, but I often don't bother. It's drowned out anyway.
What I often do is read the reviews. What's usually done is a critical review and still 5 stars. The fake reviews are pretty easily spotted. It shouldn't be this way, but in my experience it's still better than Amazon. With Amazon more effort is made to fake a review.