Highlighter for E-Hentai (e-hentai.org/exhentai.org). Supports regular expressions.
I can't replicate your bug, I tested it on the version of Firefox that you're using (49.0) and everything seems to be working correctly, even after installing an older version of the script first and then upgrading to the latest version.
Try hitting Shift+Ctrl+J (will open the Browser Console), clear the console (icon with the garbage can on the top left corner), then open the site's homepage and see if any errors pop up in the console (errors are orange-colored and have a cross on the left side). If you don't see any error, try saving data in the script.
Stopped working on firefox since yesterday update
It broke even when I tried rerolling to older version. It does not save the settings nor do clicking on highlight/filter does anything.
Every other script I have still works, and this script also still work under chrome Tampermonkey.
http://i.imgur.com/8hAVJfB.png