If there are customized key  bindings using Shift or Ctrl modifiers it may happen that an ability gets assigned to a hotkey unintentionally.  
  
Example: 
1) Customize key bindings and define CTRL-N for "Next Character" 
2) Hover the cursor over an ability 
3) Switch to the next character using the key CTRL-N 
  
Observation: 
The ability is assigned to the Hotkey "LeftCtrl " 
  
Expected: 
The character shall be switched to the next character without assigning an ability to a hotkey.  
  
Suggestion: 
I would suggest to make the hotkey assignment more explicit using an explicit key to initiate Assignment-Mode. While in Assignment-Mode the UI shall indicate it clearly and allow to switch characters and assign hotkeys to abilities. Use the same explicit key to leave the Assignment-Mode