"to comment out" before the era of programming

I have never encountered this usage outside programming, and there's no reason to expect it would have existed before then.

"Commenting out" means instructing the compiler or interpreter to ignore the text in question. The primary purpose of incorporating the instruction was to allow the programmer to insert comments which would make his code more intelligible - what you might now, if you were as frivolous as I, distinguish as "commenting in". Programmers quickly realized, however, that the instruction also permitted them to de-activate code segments for test or debugging purposes, and it is that which is the origin of "commenting out".

No such practice is called for in ordinary literary texts. Comments of various sorts may be distinguished "in line" through puncutation or a change of script or type; or inserted in margins or at the foot of a page; or banished to the end of a text. Deletions are accomplished by, well, deletion, or overstriking, or excision.

As far as I can tell from a few minutes searching on Google Books, comment out has not been used as a phrasal verb other than in the programming sense.

Here's the most interesting use of the collocation:

1689   Abednego Seller, The History of Passive Obedience Since the Reformation 97   We have ſeen Rebellion commented out of Rom. xiii.

Since Romans 13 is all about obedience ("Let every soul be subject unto the higher powers ...") I think this must be comment used in the obsolete sense "devise, contrive, invent" [OED].

Perhaps there is a similar verb to commenting out for non-programming settings, but "Comment Out" derives directly from the fact that you are using the comment syntax to remove something. The semicolon in your example wasn't originally intended to remove data, it was intended to allow programmers to make comment in their code for future reference.

Without the reference point of the commenting code syntax, the term "Comment Out" would hold no meaning.