There are 490 moderator across all the SE sites. (so you are bound to see a diamond or two.)
Yet only the three BSE mods (gandalf3, iKlsR, and me) and SE employees will have diamonds attached to our name on this site.
The three users you linked to are employees of SE (and have mod+ abilities on every site.)
Oded is a dev at SE.
Robert Cartaino is a ...