I mostly work on an iPad mini in landscape mode. With the three columns, the result is that the central content column isn't nearly wide enough.

Personally, I hate the way the right column is being used. I've been trained by years of web usage to know that the left column is for navigation, the center for the real meat of the web page, and the right is junk for when you're getting bored. In other words, the right hand column is pretty much noise on a large percentage of web sites that use it, and thus ignorable. I certainly expect to see the info for an author of a message either in the message or linked from it.

I'm guessing this is a losing argument. So how about a) making the columns resizable, or b) having a hide/show button or other gizmo for the right column. Either way, change the CSS for the author's name in the message to make it obviously clickable.