[Moonman62]

But when the pre-existing information suffers a mutation significant enough for natural selection to act upon, it is virtually always harmful.

In other words, not always harmful, especially in the case of duplications.

[GodGunsGuts]

Not so, the ones that natural selection can’t “see” are still slightly harmful, or what they call “near neutral.” These accumulate and become very harmful within our own lifetimes in the soma, and they are also accumulating via the germ lines of the entire human race, and will eventually lead to error catastrophe according to the population geneticists.

[count-your-change]

“In other words, not always harmful, especially in the case of duplications.”

What happens in duplications and what percentage of mutations would you say are harmful?