"Flatter me, and I may not believe you. Criticize me, and I may not like you. Ignore me, and I may not forgive you. Encourage me, and I may not forget you." - William Arthur

Which simply means that comments are highly appreciated... And besides, it's not so hard to leave simple messages...

“Never make negative comments or spread rumors about anyone. It depreciates their reputation and yours.”
-Brian Koslow