Can't prove the supernatural God

[Mister Agenda]

If it was something derived from another work, no fragment of the original remaining, it is mere hearsay.

Sure, but is that surprising? Anyway, it is only a problem if you prove it was added later instead of it being original or from a pre-mark source. Since you cannot do that, nothing changes and Mark suffers no undermining.

That Mark meant to put it there and left it out accidentally, which a later transcriber honestly corrected, is at least somewhat speculative. Which doesn't undermine the earliest Mark manuscript we have, but at least slightly undermines that portion of every subsequent Mark manuscript, and anything based on that part of the manuscript.

But you're right, the whole thing is hearsay in any case since it's a second-hand account by an unknown author that can't be adequately substantiated, which makes the subsequent writings based on it even less reliable.