It's just there to show whether people approve or disapprove of your comment.
There's no repercussion or penalty.
For example, if you ask for X feature on a game page, and you get -10, it simply means that the community of that game disapproves of what you're asking for.
If, on the other hand, you get a +10, it means that 10 people agree with what you're asking for.
Again, there's no penalty nor do you earn anything, it's simply an indication of how popular your comment was and don't give it any more importance.
On the other hand, if someone in particular is harassing you, that's already something serious and in that case it's best to contact support and provide all the relevant evidence.