Definitely should advise folks against using Stylish. My copy of Firefox/Waterfox auto-prompted me to remove it about a week ago, but I’m sure some folks might not have heeded the warning. All that said, userstyles.org links can still be of use: there are non-evil replacements for Stylish (such as Stylus) that can apply userstyles safely and effectively.
Ok, updated the Goodies dialog with a link and note about Stylus. I can’t remove Stylish entirely because the dark theme is hosted on userstyles.org which is owned by Stylish.