Depending on your community and their expectations I think I’d close the topic (as we do) and then if a feedback topic is started, link to it from the closed feature topic.
You retain it on the same category? How do we segregate it from other requests that are still open. Can we disable the votes after we close it but keep the voting open for others?
The topic closed icon should signify that. You could use tags as well to make it more obvious. Closing the topic will return the votes for that topic but it won’t affect voting on other topics.