Worth noting that it's easy (and probably fairly frequent) to click the wrong arrow, especially on a phone screen. I've started double-checking the "unvote" vs "undown" link that appears afterwards to make sure I hit the right one.
So that's how you tell, salutes. Sometimes I worry that I inadvertently downvoted someone by mistake. "But you can just unvote if that happens" sure but how do you tell what was voted.
Anyhow, I think if this was my forum I would put the downvote selector at the end of the comment title and have the upvote selector at the beginning.
There's no specific filter. The main effect is blending the previous frame with the current frame. When blending, I modify the coordinates and add some noise. This makes the graphics look less basic and it creates this noisy trail when things move.
Edit: Thanks for the downvote, guess I shouldn't have paid any attention to this post at all?