Does overexposing help get a better RAw file in the OMd?

Anders W wrote:

Well, it was exactly such a scenario I had in mind. You prefer to say this is still ETTR. I prefer to say it's not ETTR but that it makes sense to do what you describe anyway. Of course one reservation would be that neither you or I would ever shoot at ISO 25,600 with the E-M5, let alone shoot at that ISO without filling the "ADU buckets". From about ISO 1600 it's no better (except possibly for noise quantization errors) to crank up the ISO and expose up to the clipping point than to stay at a lower ISO and stay some distance away from the clipping point. On the other hand cranking up the ISO while retaining the same exposure won't do any harm either as long as you know where you have your highlights.

In short, we just prefer to use the word ETTR in slightly different ways, without any substantive disagreement of what it makes sense to do.

If you haven't seen it already, you might also want to have a look at what goes on at intermediate ISOs, where there are some pecularities to be aware of between ISO 200 and 400. See here:
http://forums.dpreview.com/forums/post/41988325