I don’t know exactly what fixed it. I deleted the manually-installed script and disabled all add-ons except Greasemonkey. Then I installed the script again and loaded the reader page. Now the script works even with all add-ons re-enabled. My best guess is that some add-on or other was interfering with the installation process somehow.
Update: It’s working for me now.
I don’t know exactly what fixed it. I deleted the manually-installed script and disabled all add-ons except Greasemonkey. Then I installed the script again and loaded the reader page. Now the script works even with all add-ons re-enabled. My best guess is that some add-on or other was interfering with the installation process somehow.