Maybe it's worth de-emphasising the box in some way to keep the focus on the profile posts themselves? Maybe fading the text box, or shrinking it until you click in it, or something like that. I do think it should stay at the top, though.
That requires scrolling up the page to get to (depending on screen size) whereas the current location doesn't and makes more sense. All it may need on some sites is a bit of education for the users (a HYS post). On other sites no education will be needed as the users already use something similar (Widget Framework).
No it's not. Try it on a tablet in landscape and it isn't always visible. On tablets in portrait and on mobile phones the user information box that you have put it below isn't even displayed.
The current location makes the most logical sense and it works in all formats.