To get around it for now I am using the Buddypress xProfile Rich Text Field plugin which allows an RTF field which does maintain all formatting if re-edited.
No doesn’t work either, still strips out the attribute on save. Also tried the to remove wp_filter_kses with a priority of 1– still not working though.
Ok I just worked out it’s the theme as TwentyTwelve works perfectly, the theme I am using is a Genesis ChildTheme based on the framework – so I need to find out why..