I just noticed something interesting!
A troll with bad English and 2-sentence reviews with -19 Karma has downvoted all my reviews!

I once found their review and it was obviously deserving a downvote... a "awesome coin, brought me good profit" is not called a review, so I downvoted it!
After that, they just went and downvoted all my reviews for obviously no reason... he/she is the only person who has downvoted me but you still count it in my karma score!
My suggestion: If someone has high karma or is top 20%, give their votes double power (+2 -2 karma per vote to others). Also if someone has negative karma or less than 5 and/or doesn't have a review posted, just don't count their votes.
Right now if I want to troll someone I can just create multiple accounts and downvote them to the ground... not a very fair system!