@bmjcode I pointed you to the wrong file. You should read this. And now I think it's clear: the purpose of ! is marking a string as not translatable, that is it should not be included in the PO files.

For the sake of this PR, @Pruchniakowski did it well. All the names should be marked as not translatable.

But the file credits.md contain some inconsistencies which should be fixed:

$ git grep 'Marnen' i18n/userguide/it.po
$ git grep 'macOS packaging' i18n/userguide/it.po
$ git grep -A3 'Homebrew formula for macOS' i18n/userguide/it.po
i18n/userguide/it.po:msgid "Homebrew formula for macOS"
i18n/userguide/it.po-msgstr "Formula Homebrew per macOS"
i18n/userguide/it.po-
i18n/userguide/it.po-#: ../../frescobaldi/userguide/credits.md:46

I'll open a new issue for this.

Originally posted by @fedelibre in #1993 (comment)