In my personal opinion, reputation systems that allow downvotes are always easily gamed and abused, and trolls tend to use them to their advantage. Real reputation is not a number, it's a relationship, and whether the number is there or not then reputation will still exist. So I would suggest removing it unless it can be limited to upvotes only.
A user in the other thread mentioned this "thank you" plugin which may work well as a replacement: https://community.mybb.com/mods.php?action=view&pid=360
A user in the other thread mentioned this "thank you" plugin which may work well as a replacement: https://community.mybb.com/mods.php?action=view&pid=360