What is the reason for wanting to do this?

I've done it when I've found a colour film, either in the back of a draw or in a camera from eBay and I don't know what is on it. Could be nothing, or rubbish, or something ... unwholesome so I've chucked it in rodinal just to see (and of cause it always has wonderful pictures on it that I'd wished I'd got processed properly )

Quality wise I've always got hard toprint rubbish with no redeeming features that I can see...

Processing a Black and White C-41 film in BW chemistry is a different ball game altogether, there can be very interesting aspects to this.