You can modify your regex to only match when it's not a shortened url - then the short one will redirect to the real www.reddit.com address, before the redirect

You can modify your regex to only match when it's not a shortened url - then the short one will redirect to the real www.reddit.com address, before the redirect matches. (Don't have the correct regex on hand right now, as I changed browsers and decided to use Old reddit redirect extension instead of scripting, but it worked in my previous browser)