[count-your-change]

In deed it is a reply. Jesus is responding to their obvious fear and that's what the term “reply” means, a response.

“Young’s literal has it right with the exception of his parenthetical addition where he, too, tries to smooth it out.”

I don't know what you mean by “smooth it out” but there's a reason why Young's is called ‘Literal’. The addition of “he” brings the literal Greek closer to English while keeping the literalness. He is not translating ego eimi as a name or title or any such thing.

[xzins]

It is not a reply. They did not say anything to Jesus to which He replied.

It is a response to their fear, and the literal response makes perfect sense in the context of the Gospel of John. The response is “I AM!”

He’s walking on WATER for Pete’s sake (pun intended.)

:>)