Usually I wouldn't accept a job that seemed a little dodgy or was lacking in info, but as I said in the OP, I worked with this client on another job and although he was a little slow to respond, the experience was positive and I had no reason to suspect this second job would be the disaster it was.
He did fund the milestone, but because I felt the first draft needed a little extra information about the specific project, I sent it as an attachment rather than officially submitting it. I guess I was trying to be a good hire, letting him know that in my professional opinion, I had made it as good as it could be, but it would be better if he sent me some extra info.
Why do you suggest removing the URL?
Good answer in your feedback. You only need to remove urls if the link gives personal contact information, as this is against Upwork's ToS. (I don't think yours do though).
Catherine - Do NOT refund a single cent to this client. If you do that, you are teaching him and encouraging him to continue this stunt with any freelancer that he hires. It almost comes down to - you're paying HIM to do his work.
Almost everyone who loses a dispute will give a horrible 1 star review with false feedback. You could respond to his feedback with just a few lines. " Client has lose dispute through arbitration process and as clients usually do when this happens, is to vent his displeasure through a review as given above."
You should respond to his feedback and state your case. In my experience this can be enough for you to get your foot in the door with future clients, which gives you the oppurtunity to prove that you are competent despite the negative review.
Personally, I think that a libelous review (with the YOU pronoun) reflects back on the character of the one making the review rather the person to whom the review is intended for. I am fortunate that my clients give me balanced reviews. At the end of the day, I will have to ask myself about the quality of relationships that I've been forming in the marketplace.