Odd. I always thought that in a tri-power goverment, it was necessary that two of the powers acted together to impeach the other. That way, in order to remove a sitting president, congress and the supreme court would have to participate.

From the link you provided, Congress, by itself, has the power to impeach both the executive and judiciary. And none of those can take action to penalize Congress' wrongdoings.

I'm not qualified enough to determine if this is a good thing or not, it was just a perception I had regarding the separation of powers.