Most of the time I'm a very happy vim user. Vim has superb support for inputting all kind of characters, see :help digraph and :digraphs. But from time to time I need to input accents etc. in other GUI apps.
A long time ago xorg in Debian did default to use deadkeys. I remember that I was quite annoyed by it, because typing ~/ required three key presses. However, somewhen in the past the keyboard behavior was changed to nodeadkeys which makes it kind of impossible to input accents as in é, è, or â. What's even worse, I didn't manage to override xorg's auto-configuration of (**) Option "xkb_variant" "nodeadkeys, no setting of Option "XkbVariant" "nodeadkeys" did help.
Running setxkbmap de restored the dead keys for me. I should add that my system uses locale de_DE.UTF-8. This will be ok for some time, however, I think I really want to use the "xkb_options" "compose:rctrl" option, at least for the tilde. Btw, I'm perfectly aware of xmodmap, but I really don't like to mess around with it for such a simple requirement.