The seam in my granite counter is also in the middle of the sink. It's the way to get the shortest seam. You don't even see the part behind the faucet. I don't know about marble, but granite seams are sealed with epoxy. I don't think there is an issue with water splashing.

The chips are another matter. The stone shouldn't be chipped before it's even put on. That should be addressed. If the chips aren't too big, they may be able to be smoothed down. If they're big, then you shouldn't have to accept it. So yes, I'd make a big fuss about it.

Call your fabricator, you should not have any chips on a newly installed counter. They should be able to fix it.

The middle of the sink is the ideal place for a seam as it is the least visible place. So, no, I wouldn't complain about that. The chips--it depends where they are and how large they are.

No chips! I would definitely complain. They installed my island and the two corners were chipped during transport. The fabricator sent up an expert who did epoxy voodoo magic and you can't tell. Now mine were on the bottom edge. If it is on the top edge of the counter top, I would worry about it being more likely to chip again.

Word of warning - marble chips - especially around the sink, so tell everyone to be careful about putting heavy pots and the like in the sink. Makes me wish I had gotten the farmhouse sink.