Lets say a person asks a question that is on its way to being closed. For simplicity, let's say as off topic. Then someone answers a perfectly valid answer to the question as asked. Within the world of the question, it's a helpful answer. But within the site, it is not a helpful answer. Is it best practice to upvote such an answer as helpful, as it does answer the question?
This would apply equally to after the close-voting was finished and the question was closed.