Vote count before you vote: 2But you aren't. You are moving it by 2. And it's inconsistent.
Vote count after you vote down: 1 (net change: -1)
Vote count after you vote up: 3 (net change: +1)
Vote count after you vote down, then up: 3 (net change: +1)
Vote count after you vote up, then down: 1 (net change: -1)
The net effect of you voting is only a +1 or -1. Remember, you don't know who else clicked the vote button on that same post just before you did. When you load a page, the current vote loads. If you take a minute or even a few seconds to read a post and vote, others could have voted during that time. The vote counter doesn't dynamically update every time someone votes; it does only when you vote or refresh the page.