From my understanding a little over full in most cases isn't that big a deal. By little I mean .5 quart or less. I wouldn't be comfortable at a quart over. At some point the oil is going to be severely getting into the rotating assembly in ways that it should not. At some point you would get so much oil in it that it would severely damage the engine possibly.
This is an old thread, but I'm curious to see what more experienced people have to say about it.
There were some people at a gas station I grew up near, a very long time ago, that just kept buying oil and going out in the parking lot adding oil. They added oil till it was FULL. I mean full up to the valve cover lol. They tried to start the car. It didn't end well.