There are some keystrokes that are quite painful if you type them over and over. The worst ones are those where your thumb has to wander below your palm. On my german dvorak keyboard M-q (which runs fill-paragraph in emacs) is such a candidate. But all one-handed keystrokes can be a source of RSI.
Today some newsgroup posting pointed my attention to the topic of sticky keys. With sticky modifier keys, if you want to type C-x M-a Z for example, you can instead type its linear form Control x Meta a Shift z. As I said, you can, but you can still use the normal press-keys-in-parallel variant.
Ok, so how do you get sticky keys? For the linux console you have to edit your keymap. You have to replace the symbols Control, Alt and Shift with their sticky counter parts SCtrl, SAlt and SShift. I did that for my custom German Dvorak Type II keymap you can fetch from http://www.tsdh.de/cgi-bin/wiki.pl/Configs.
For X11 you have to get the AccessX utility or use the control center of your desktop environment, if you use one and it provides an option for sticky keys. KDE and GNOME do AFAICT. The command line AccessX tool ax explains itself with ax help.
Happy typing. ;-)