Hello,
My account is from 2008, and someone just told me that it's supposed to have a + sign next to my name. Is that true? and if so, where is it?

Only the users who purchased Toribash when it wasn't free to play have oldschooler sign - it's not just related to account creation date.
If you've still got a registration key which (for whatever reason) isn't connected to this account, please let us know.