Idk if Fabio has more information than me to confirm its gone-ness, but I know that in the past you had to PM Rukario and get him to add you to the other usergroup, that still has your supporter tier but an unstyled username, and then you could switch between the two in the User CP.
Yeah it was taken off moderators due to cases of switching between two status' which isn't good for a moderator (being supporter one minute, and a mod a next), so I assume it'd be the same for smods. If you get 5000 posts and get put in the blogger usergroup then become a supporter you'll have this option by default, too.
Like I said, you have to PM Rukario to get him to add you to the other usergroup before you get the option to switch between them. By default, you're only added to one usergroup, your supporter tier. By request, you can get the special one where your name is styled like a normal member. But it's only by request; you don't get added to it automatically.