Are you positive your friend didn't say "simile"? I've read Eats, Shoots & Leaves, and I can see how the book applies to similes, but not to synonyms. Or maybe your friend just misspoke.
I have no clue at all how anyone could read your writing and know anything at all about synonyms.
It was sent in an email... So unless he can't spell simile :-/
I'll see him at some point next week so I'll ask him.
Shibby