Update!
2.4
+Added option to disable signature autoembed thanks to Arantor for the method
It's a very useful mod, thanks! Alas, I'm not able to use the "Disable embeding of signatures"-part.

Meaning, I tick the box and click "Save Settings" and the box is unchecked again.
Forum is 2.0.7, the installed SAVE is listed as v2.3 in the package manager (though I installed the latest version).
Settings.php is chmod 644, folder Sources 755 - if that is of any help.
I don't know that much about programming. So, let me know, if any further information might help to locate (and ideally fix) the problem.
EDIT: If I'm reading
Sir Cumber-Patcher's posting correct, the reason might indeed be that settings.php (containing the subs.php) is chmod 644, right?