Whohoo, I gave Atom.Io another try and found a solution  workaround to my @ sign problem:

To fix my problem, I had to unset the keybinding for “autoflow“:

1. open ~.atom\keymap.cson

2. add following lines to the file:

   .platform-win32 atom-text-editor, .platform-linux atom-text-editor':

   'ctrl-alt-q': 'unset!

3. restart Atom.io

Sources: corelgott.de