I think it is controversial because there is no clear cut answer. We are not commercial hatcheries and don't have the products, equipment, experience, or techniques they use. And there are so many different variables involved in hatching it is hard to be sure how one specific thing affected the hatch. Commercial operations don't just "wash" the eggs. They wash them in a specific product using a specific technique. They don't just clean their incubators they sanitize them.
Brinsea does sell a product to use to wash eggs for incubating. I have not tried that product or seen the instructions that come with it. I don't know what that product uses to kill the bacteria, clean the egg, or if it has something in it that recoats the egg, taking the place of the bloom. I don't know if it is true or not, but I've read that the oil on a broody's feathers has a sanitizing effect on the eggs. I just don't know what to believe.
When eggs are incubating, the humidity and temperature gives a perfect climate for bacteria to reproduce. That's the big thing you are worried about. If the egg is dirty and has bacteria on it, then that bacteria might work its way inside the egg. If wash water is dirty then that dirty water can soak through the shell and carry bacteria inside.
I can't tell you what to do. I think it has to be your judgment call depending on how dirty the eggs are. If you judge them to be dirty, I think I would rub them gently with fine sandpaper and try that. I'd also get the incubator as clean as possible before starting incubation but you should do that before any incubation. Then I would do a smell test on them as they are developing, removing any that get to smelling funky.
I'm not saying this is the right thing to do, since I don't know. It is what I would probably do.
Good luck!!!