I was looking at a batch of epubs and wondering how they were made. Opening in Sigil I could not find any declarations of the software used to make them in file headers or OPF file.
Then I opened one epub as a zip and looked in the OPF. This had a line in the metadata section:
<!-- Created by Jutoh 3.13.5 at 21/04/2022 17:22:31 - config "Epub" -->
Opening the epub in Sigil, this is not shown, and if the epub is saved, it's lost.
Sigil leaves its own mark like this:
<meta content="0.9.13" name="Sigil version" />
<meta property="dcterms:modified">2022-04-02T17:43:56Z</meta>
And Calibre like:
<meta name="calibre:timestamp" content="2017-05-05T17:14:23.743000+00:00" />
<dc:contributor opf:role="bkp">calibre (2.83.0) [https://calibre-ebook.com]</dc:contributor>
"bkp" being "Book producer".
Annoying that there is no standard for the creating software, when there is a myriad of esoteric creator/contributor codes:
https://www.loc.gov/marc/relators/relaterm.html
Maybe that's why Jutoh never bothered to try.
So, I know that it's perfectly correct for Sigil to ignore such HTML comments, but in the interest of preserving info that someone thought was important enough to put there, maybe on opening these can be converted to valid metadata. Sigil already does a lot of fixes on non-standard files on first opening.
This seems to work:
<meta content="Created by Jutoh 3.13.5 at 21/04/2022 17:22:31 - config "Epub"" name="comment" />