My point for bringing them up was to (hopefully) illustrate how it's not always clear whether something is or isn't man-made.
You said:
"But we can look at some random artifact with it stamped on there and immediately recognize that it was not formed by natural processes."
I realize you were talking about cuneiform writing and not undersea "roads," but I'm curious by what process one could "immediately recognize" that something was or was not formed by natural processes.
Right, and I understand that. My cuneiform example was intended to show that there are examples of things we could find that we would know almost immediately were artificial. I was saying that to illustrate that it wouldn't be unscientific to make such a conclusion. And so if there are cases when we can see it right away, there are also going to be cases, like the "Atlantis" example, where we should be able deduce it through more in-depth (no pun intended) investigation.