Upvote/downvote arrows are too close togheter to comfortably use on phones, especially that the actions are not possible to reverse.
Some UI idea is needed here imo. I like what Reddit is Fun app does: you need to touch the post and then upvote/downvote appear below it next to each other. Unfortunately that wouldn't be natural for desktop/mouse users.
As it is now, downvote rights which just appeared on my account make it that I can no longer upvote anything on mobile, risk of accidently hitting the wrong arrow is just too big.