Since I've been frequenting this website a lot on the past months, I can say that it is somewhat interesting on how people tend to avoid down voting or up voting here. I thought possibilities to help out with this issue (on a indirect manner):
Bonus for commenting and voting:
If you up vote or down vote an answer or question and comment on it, you may have an additional small bonus point (+1?) for it. This would make the engagement more rewarding, welcoming more feedback on a answer or question (also, this system it would not differentiate if the provided feedback on the comment is criticism or a compliment).
Approved bonus by the asker for very helpful comments or answers aiming to improve the question:
Sometimes a user may struggle with text construction or even with the English language. Sometimes they can't even explain correctly a concept or mechanism of the game due to being extremely inexperienced with Tibia. A helpful comment or answer (even one that ended up down voting the question) would be very appreciated in order to make the website more busy and friendly to newcomers (pay attention that such bonus would only be granted if the fore mentioned helpful comment made a vote on the question). An extra point to the asker that selected the answer or comment as helpful would be realli good ot implement on this case here.
Extra badges related to voting that can reward you additionally with points once you unlock the badge would be a great feature as well.