I think the portrayal of Regdar with third person Regdarspeach came from Monte Cook's Miniatures Playhouse, where he's also always mistaking Lidda for his kid sister.
Me drowdude thinks that has something to do with The Rock. Me drowdude finds Redgarspeak entertaining, but me drowdude likes to refer to it as "Grimlocktalk".
Your PC might not earn the noble prize but with an 8int (forrest gump level) he's not the brightest bulb in the bunch but he doesn't have to talk in 3rd person. Make his speech slow or slurred like he is furrowing his brow to make a sentence up and make it right. I knwo folks that are like that and they never refer to themselves in teh 3rd person "Bob thirsty so bob get beer for you and bob!"