I volunteer at a tree perserve. Our oldest oak tree has been marked with knives and the outer layer of bark has been removed. aprox. 18'' by 29''. I have been asked to try to find a way to cover (mask the damage) .
Ancient Live Oak Damaged by Names Cut Deep Into Bark
Certified GKH Gardening Expert
I am sorry to hear vandals did this to your tree. You can't exactly hide the damage and the tree will repair itself, but you can make it so that the names are no longer there. Method 2 at the bottom of this article explains how to do that to the bark: https://www.gardeningknowhow.com/ornamental/trees/tgen/repairing-tree-bark-damage.htm
Even on the parts that are cut deeply, you can cut a little deeper into the phloem and the cambium (deeper wood) layers to remove the deeper wood that would show what the words say. Do this just enough to obscure the words, perhaps just removing the interior of the letters. While it is awful they did it to such a grand old tree, fortunately, because it is older, it can take such damage and recover.