[milesvp]

You may not know this, but custom orders slow down service sometimes by an order of magnitude.

I worked at a takeout teriyaki joint in college, and it was as fast a food as you could find. There were 5 menu items, and I could really get in a rhythm dishing rice and chicken and coleslaw. But as soon as anyone asked for something non-standard, then suddenly muscle memory was gone, and I actually had to think about what I was doing. Just asking for no salad could halve my serving speed, especially if they asked for at the wrong time of doing the order.

I can only imagine how much worse this is in a setting with multiple people and multiple handoffs.

On top of that, if the restaurant isn't being run like a short order joint, they're going to have other issues with mixing and matching menu items, like now they may have 2 less dishes they can serve, because, believe it or not, ordering for a restaurant can be a very precise thing, and they'll likely order quantities proportional to the menu ingredients. I'm not saying don't do this, but I am saying be polite when you request these kinds of things, and be willing to accept "we can't do that" as an answer.

[beerandt]

I'm not arguing for or against allowing special orders. But that's on the manager, not the customer.

The server having an issue with it (when the manager doesn't) is a problem, and blaming customers for making requests is a problem, especially if policy is to allow them.