Update: I made the action, but there is something 'is preventing it from working'.
To test, I added a (default) 'User logged in' content rule.
For this, I used action 'Notify user'.
- If I go to front page and log in, no message is shown to the user.
- If I go to another page and log in from there, no message is shown to the user.
- If I go to (for example) /news/edit (and log in when asked for username/password), the message is show (correctly).
UPDATE: This only happens on 'localhost', if I have a 'proper URL' it the message is shown.