What is the class of the product with the most reviews?
most review refers to MAX(count(comments)); high class refers to Class = 'H'; medium class refers to Class = 'M'; low class refers to Class = 'L'
SELECT T2.Class FROM ProductReview AS T1 INNER JOIN Product AS T2 ON T1.ProductID = T2.ProductID GROUP BY T2.Class ORDER BY COUNT(T1.ProductReviewID) DESC LIMIT 1