I have two chatterboxes here. Lucy is just a loudmouth, and Meezer Girl is a Siamese ('nuff said, right?
). Lucy has high-pitched normal meows 24/7. It's like she works for a cable news network, because she constantly has to update us on everything. Meezer Girl just sounds grumpy and "growly" (even though she's one of the most pleasant kitties alive) all the time. Neither one ever sees fit to shut up while they're awake.
Do you let your kitty sleep with you? Mine tend to shut up for the most part when we're in bed. They might yell at us if we move them around too much, but they're generally quiet in the bed (until breakfast time, anyway).
I don't really mind cat-talk, so it's not a big deal for us (actually, it's why we got the two little bullhorns). Siamese are notorious for their voices, so I'm not surprised your boy has a lot to say. If he's yelling all night, I imagine he's just not tired enough at bedtime. Wear him out and take him to bed with you.
If he's just a loudmouth, and you really don't want a loud cat, and you think he's just meowing for no reason, I guess you could take him back. I hate to say it, but there are plenty of quiet cats in the world needing homes, too.
Everyone has their own preferences. I don't like timid cats who hide all the time, so I won't keep one. My mom has a very timid scaredy cat who probably hasn't been seen by more than three people (not counting the vet) in over four years. She adores her, even though she only sees her long after lights out (the cat is very affectionate when my mom's in bed, but don't even think about turning on a light or letting anyone else make a peep within earshot). Everyone has their own "deal breakers".