??? Seriously? That’s the rationale behind it? Don’t get on in public places if you don’t want it seen. I can’t see a good reason for this feature to exist. You can always just logout and thus none of your info would appear. Just hiding it from the top is meaningless. As when you post a new topic or reply, your avatar will appear then.
You could always use a custom stylesheet within your browser to hide your top bar info, if you really want to, but I think it is a waste of time and effort.