Prevent ALL templates from being rendered directly? I attempted to set the privateTemplateTrigger to an empty string in my config/general.php file, because I don't ever want Craft to serve up a template file on its own just because a visitor happens to put in a URL that matches its name, and I was hoping to avoid prefixing every single file in my /templates directory with an underscore. Unfortunately doing so breaks several CP pages (like Globals and Plugins)...

I'm guessing it's because some CP files are relying on this feature? Surely there must be some way to disable this "direct rendering of template files" thing that doesn't break the CP?
This is very, very simple to do... just put every single template into a specific folder, then prefix the folder with an underscore:

/craft/templates/_everything/


Template files beginning with underscores are hidden, similarly, template folders beginning with an underscore hide everything inside.