I flagged one of my questions Overriding views-view-fields.tpl.php to request that mods move it to http://drupal.stackexchange.com but I think my request was denied/ignored. I'm not too sure how to tell but it has yet to be moved. Would it be wrong for me to re-post the same question on http://drupal.stackexchange.com? What's the proper etiquette for handling this?
You shouldn't cross post.
What you've done is correct. The moderators will have seen the flag - it could be that the one who dealt with it didn't agree, but I would take a request from the poster as meaning I should migrate straight away.
Raising the issue here is the next step - another mod should review the situation.
If you do cross post it means that when the question is eventually migrated it will have to be merged, which is more work for the moderators on both sites.
Cross-posting the same exact question is not what you should do. If you were asking the question on SE sites with different topics, then you should adapt the question to better suit the site where the question is being asked. In the case where the same question is on-topic in both the sites as it is, I would suggest to flag it for moving it to the other site; if the question is not being moved after X days, then I would suggest to post a question here, as you did.
Keep in mind that normally (or generally) they don't migrate a question that is on-topic on a site to a beta site where the question is on-topic too.