Leave them the way they are....
.....so this doesn't happen....
That is out of the scope of this question for two reasons. First, she wasn't trained as an iconographer, or art restorer, or anything similar, as evidenced by the results of her work. Second, she was working on the original, not a duplicate of it.
The icon of the Mother of God in the post, known as Vladimirskaya, or Mother of God of Vladimir, is one of our earliest surviving icons, painted in the 1130s. Far from being "untouched", this icon has indeed been retouched more than once over the near thousand years of its existence. It has survived much, including fire, during that time, but it is telling, and heartening, that the parts which remain original and intact are the faces of the Virgin and the Christ-child, His hands, His left foot, and her left hand which embraces her Son, and, at the same time, points to Him as the Way to salvation.
Many an iconographer has attempted to paint a copy of this treasure. Few, if any, have come close to reproducing the majesty, compassion and poignant love in the Virgin's face which graces the original. Some things are best left alone.
I don't see anything wrong with leaving the original alone, but why is it that the duplicates, and hence the exact copies of that icon sold (for example at http://www.legacyicons.com/products/theotokos-of-vladimir-legacy-icon
) reflect the same damage without having been damaged themselves?
Notice the wood is flawless, and the icon itself (the image) is a print that has been affixed to the wood. If you're not going to be appreciating the full splendor of the icon in its original form, why would you be settling for something that reflects only a part of that, despite not having been put under the same conditions?
Another famous icon which is very badly damaged is the Savior of Zvenigorod, painted by St Addrei of Radonezh (AKA Andrei Rublyev) as part of a deesis (supplicatory) series for the Cathedral of the Dormition in the town of that name. Sadly, only three panels survive, the Archangel Michael, and Apostle Paul being the other two, and the damage on all three is serious. Yet this Savior is regarded by most, if not all, iconographers worth their salt, as unreproducible, even in reproducing what remains, let alone attempting to reconstruct what is missing. They are, quite rightly, daunted by the utter sublimity, subtlety and power of the original.
Here is what an iconographer I know has said about seeing the original Savior. There is much wisdom and food for thought in what he says:
No reproduction can capture these qualities, nor could any copy. When you see the original, you are overwhelmed by it. You look at it trying to figure out how the effect has been achieved but in the end you just give up. The important thing is that, despite being in a gallery, you can pray in front of it. Thoughtfully, they have put benches in front of it so you can sit and contemplate it.
Unlike some icons, or singing, which are beautiful and brilliantly done, you don't admire its aesthetic beauty. Rather, its beauty serves, and is subordinate to, its spiritual beauty and power to work on the soul. The other icons in this series hang either side of Christ, that of Archangel Michael on the left and St Paul on the right. These too have great power. The famous Holy Trinity icon is in the same room. The original Mother of God of Vladimir used to be there but thankfully is now in a church attached to the Tretyakov. This icon by contrast has been much copied but rarely very well.
Exactly my point - you don't get to the same place of contemplation, awe, and presence in being in front of a duplicate of the original, even if it is pixel-perfect. Not everyone can actually get to see the original. The contemporary copy you linked is not anywhere close to bringing that out, BUT, it remains more full and visible in the depiction of Jesus than the original does - rather than being a face that is shown, it is a face, a body, and clothing.
To be frank I also do not understand why to make icons that look damaged despite them being brand new. Isn't destroying icons condemned somewhere?
As far as I'm aware if they're no longer fit for veneration they should be burnt and buried in a place where the ashes will not be disturbed. I don't know if this is correct or not, though. I figure it'd be best to ask a priest what to do with the icon should it reach that state.
Under no circumstance can such an icon, even one that has not been blessed, be simply thrown away. A holy item, even if it has lost its original appearance, should always be treated with reverence.http://www.stjohndc.org/Russian/what/WhatE/e_PrayerCorner.htm
If the condition of the icon has deteriorated with age, it should be taken to the church, to be burned in the church furnace. If that should be impossible, you should burn the icon yourself, and bury the ashes in a place that will not be sullied or disturbed, e.g. in a cemetery or under a tree in the garden.