The following question is pretty obviously (at least to me) unsalvageable, the edit was made to point out how badly written the question was and doesn't improve it at all (apart from to make it even clearer to the OP what was wrong with it).
Can anybody come up with a reason for the reopen vote?
Definitely a valid question. The question is, as you said, basically unsalvageable, apart from massive editing. Sean, like you said, just edited to clarify that there was some conversation material, some off-topic questions, and just generally to make it easier to read.
So why the re-open vote? Tough question. There are multiple possible reasons: As Andrew pointed out, it can be accidental, but sadly, occasionally people will see that the post is better edited than it was before (or at least, better formatted) and think, "Aha, that looks nicer than it was. I guess we could reopen that," without taking time to seriously give the post a read.
Moderators do have tools with which they can determine if this is happening in a serial way from a single account, and we do have the ability to give a given user (after we have satisfied ourselves that it is definitely merited!) a review ban, during which time they will be unable to review close / reopen / whatever votes.
It's a good reminder to all of us that review queues are for just that - reviewing. The purpose of the review queues is not to amass badges, it's to give posts that are sent there a serious examination. Is this post on topic? Is it clear? Is it specific enough? Failure to do this is counterproductive and self-destructive. Which is why, if this kind of behaviour is repeatedly seen from a given account, as moderators, we apply review bans.*
When you see this kind of behaviour especially on a small site like this one, just flag for moderator attention and move on. (Be specific and detailed with any evidence you can see — don't just flag with This post should be closed why aren't you closing it.) One reopen vote won't make a huge difference in the grand scheme of things.
*Obviously, this does not completely solve the problem, since users can still simply vote to reopen without going through the review queue. Without going into detail, there are other tools available to moderators to deal with these situations.
Updated
Apparently the question is asking about any reasons why the question got a reopen vote on "reopen" review queue, and that's almost impossible to know unless you ask the voter directly.
As a 3rd-party and even though I'm not an active user on here, but based on my experience on other SE sites, I certainly couldn't see any reasons to reopen that question. The edit didn't try to salvage the question, thus it should be leaved closed.
Any possible reasons are thus speculative:
Original answer
The question was put into the reopen vote automatically because it's edited while it's being put on-hold.
As per FAQ on Meta Stack Exchange,
What does it mean for a question to be on hold?
If a question has been closed (except as a duplicate), then for the first 5 days, it is marked as “on hold” rather than “closed”. This is meant to convey that the question requires improvement and may be reopened if improved. During this period, if the question is edited, it will be added to the reopen queue. Other than this, there is no functional difference between “on hold” and “closed”.
So, please be careful of editing on-hold questions if you can't be sure to salvage it. Otherwise, the chance for OP to get the question reopened after editing it will be wasted (though, users with "close/reopen vote" privilege can still initiate a reopen vote manually on it).
I see a 2nd question (not a clear case for deletion, but still in need of work) is gaining re-open votes after a minor edit. As per the suggestion above, I flagged it.
