So recently I liked a comment, but then I realized that it was the wrong comment I up-voted! And I was presented with this screen
Why is this?
This is a network wide feature. Basically, as this post mentions,
"We do not want flip flopping, nor do we want people to un-upvote stuff from the past. The only use case is undoing a mis-click."
You basically have one minute to decide if you clicked on something by accident, and then it is considered to be locked in. In the case of comments especially, they're considered to be ephemeral and subject to pretty free deletion in a lot of cases (especially if they're off topic, etc), so there's not really a huge need to have the option to extend this timer, etc.