It's probably IMDb experimenting with enabling site-wide HTTPS. Once you get redirected to a single HTTPS page on IMDb, all other links opened from it are going to be HTTPS too.

Most userscripts are not prepared to work on HTTPS pages, but it's a very easy fix.

Heh, backward compatibility is definitely something I didn't bother with at all. :)

I've decided against publishing a proper userscript on OpenUserJS/GreasyFork, and instead just put it into my GitHub repo: link.

I'm not fully satisfied with it (some parts are too hacky, and you still have to edit the code to change colors/priorities), but it will do for now. I'm using this version myself, so as long as I am watching movies I'll keep this fork updated.

Hi!

I've been using your very helpful script for a very long time (three years at least), and lately I have been rewriting it in modern JS (ES6+) for practice. I had a small fork of my own before that where I added a way to assign priorities to lists, so I thought remaking the rest of it around that feature would be a good idea. I went the "Ship of Theseus" route so that as much of functionality and corner-case handling as possible would be preserved, so it should look and feel the same as the old one.

I'd like to post my fork, keeping the copyright notice and license and all. I see it's GPL v3, but I thought I should ask if you are okay with that anyway.

The script doesn't recognize movies that have a double quote character.

For example:
http://www.imdb.com/title/tt0095675/
Mujeres al borde de un ataque de "nervios" (1988)

A fragment from an exported csv:
"1753","tt0095675","Wed Dec 28 00:00:00 2011","","","Mujeres al borde de un ataque de "nervios","Feature Film","Pedro Almodóvar","5","7.6","90","1988","comedy, drama","21371","1988-03-14","http://www.imdb.com/title/tt0095675/"

I assume the issue is with the regex from the function downloadOK, which doesn't expect badly formed CSVs from IMDb:
var regex = /"tt[0]*(\d+)","[^"]*","[^"]*","[^"]*","[^"]*","[^"]*","[^"]*","([^"]*)","([^"]*)"/;

This change seems to help (unless there's a movie with a title like "Breaking", Bad CSVs, in which case the regex will probably need to match whole lines up to the line break):
var regex = /"tt[0]*(\d+)","[^"]*","[^"]*","[^"]*",".*?","[^"]*","[^"]*","([^"]*)","([^"]*)"/;