I mistakenly downvoted a question and would like to change it to upvote. However, the ELL system requires the edit first before changing. Why and for what purpose? Anytime I try to change from downvote to upvote, a message appears "You last voted this question **** minutes ago. Your vote is locked unlesss this question is edited". Is this function necessary?
This is not something we can reconsider as English Language Learners; it's a network-wide feature known as vote lock. That answer on Meta Stack Exchange provides some rationale behind this decision:
This helps to prevent irregularities in voting. If I could go back and take away every up vote I ever made, more than a few people would see a 1k + drop in reputation. If you thought the post was good, or not good for the duration of the grace period, the system assumes you knew what you were doing when voting either way.
This is in order to help curb the tactical down-vote problem.