So bear with me. I am no historian or history student, I just take great interest in the subject during my spare time. Thus, my question is : through the ages, Damnatio Memoriae was used as a form of punishment to completely erase the condemned person from History. In that case, how do archaeologists find out about said people and reconstitute the facts?
How did we come to unravel the (partial) truth about Commodus, Shepseskare, and other rulers that were "erased" from History?
As is mentioned in the comments to this thread, which I think realistically should answer your question more or less without further input, damnatio in the Roman world was never intended to erase an individual's historical existence--a truly impossible task for anybody worth erasing--but to isolate and remove the individual's public persona. Quite different things.