Profiles are now entirely site-specific so you have two options - laboriously maintain site-specific profiles, or use a common profile everywhere. You can't maintain a few site-specific profiles and have a universal profile for all other sites due to inconvenient editing options - any change must be either reflected universally (overwriting all the site specific profiles) or else on only one site.
Have both a universal profile (which is shown everywhere) and a site-specific profile for each site. That way you can edit universal information about yourself, and also separately edit info about yourself that's only relevant to one particular site. Both the universal profile and site-specific profile text will be shown (one appended to other) if you browse that person's site specific profile