In Mac OS X there are ways to input punctuation marks by combination of some keystrokes. For example, Alt + ; inputs a precomposed ellipsis character (…, U+2026). Alt + [ opens a curly double quote ...
I tend to use Ctrl+Shift+Alt for my customized system-wide keybindings. When I tried Ctrl+Shift+Alt+U it printed an underscored u and waited for more keyboard input!... Some keys were accepted and ...