It will be less confusing for the user if he says that the votes on a post only increased by 1. Let's say that User 1 goes to the site and sees that a post has 10 votes. Then User 2 loads and page and immediately votes that post up. And then User 1 votes up the post. I think it would make sense for User 1 to see the vote count increase from 10 to 11, rather than 10 to 12, or else the user would be confused.