I don’t know what happened, but after I read your explanation I tried again and it worked like it should.
What happened on my first attempt: I clicked “Verify and share” and the “Shareable verification link” that was generated pointed to the “old” tx, the one I hadn’t signed. When I recognized that I copied the transaction script from the box and manually replaced it in the “Shareable verification link”.
I tried again just now.
I clicked on @Dhume’s link,
verified the output address and the amount (pretty much all I can/have to verify, right?),
hit the “Continue to Sign” button,
signed it with my privkey,
clicked the “Verify and share” and
recognized that the site that was loaded, contained the proper content (I realized that it showed “Signed: 3” where it previously showed “Signed: 2”).
So there was an error on my end, but I don’t know where.
I’m so happy about this site you created, that it provides the FLOT with an incredibly useful and convenient access to signing transactions!
The cointoolkit can speed up the signing process by orders of magnitude!
If you have your privkeys at hand (safely stored in something like Keepass for Android or iOS), you can sign transactions from your mobile phone!