Did you mean to post that somewhere else?
I think kvn might be referring to a CSS popup when you hover over the downvote button there, a quick reminder about what the button is really for, sadly easy to overlook in the heat of the "I don't agree with that guy!" moment.
Unfortunately, you're incorrect. League of Legends players are known to be very...salty. The entire community is known as THE worst gaming community right now. Their reddit section reflects that. I once made a comment about how I believed that I didn't like one of the characters, and I got 50 downvotes overnight.
To clarify, I just guessed that you were referring to the popup that reminds people what downvotes are for. I never said I thought that sort of thing actually worked.
I just don't think friendly reminders work on people who downvote to disagree.