Possible Clues:

• Ridiculous ringing Mother using the vernacular
• Man with papers, reportedly Greek native?
• Such expressions may be meaningless, academic admitted
• 'I can be of service!'
• Graduate in absurd situation using language like a native
• Peculiar to a dialect
• Stupid to keep mum regarding one variety of language
• Using common language, mum punches halfwit in charge
• Barking welcomes parent using dialect
• Foolish to arrest graduate with a peculiar style