Hides all letterboxd reviews with fewer than a certain amount of stars (default: 3). Does not hide your own reviews or reviews you have liked. Options "minRatingToShow" and "hideReviewsWithoutRating" available in code.

Also check out:

• Goodreads - No Negative Reviews https://greasyfork.org/en/scripts/470806-goodreads-no-negative-reviews
• RateYourMusic - No Negative Reviews https://greasyfork.org/en/scripts/489467-rateyourmusic-no-negative-reviews