As written, that wouldn't actually upvote anything; it would evaluate the variables upvote and arundel-post and build a cons cell containing them, which would serve as the value of the expression. Since we're talking scheme, functions called for their side-effects customarily end with an exclamation mark. I would write something like this:

(upvote! arundel-post)

Here endeth the extreme pedantry! And now, before I forget, I'm going to go upvote the post instead of just talking about upvoting it.