Short answer

It is possible to switch off the integrated help by setting the AsciiDoc Document Attribute arc42help to false, e.g., in the config.adoc file which is part of any AsciiDoc based arc42 template.

Longer answer

AsciiDoc enables customization of contents, layout, and processing by so-called document attributes. These attributes can be defined in any place of the AsciiDoc documents. However, most often, global attributes are defined in the document header. For arc42 the document header includes a configuration file which contains settings which are customizable by the template user. By default, arc42help is switched to true, so that the generated HTML or PDF contains the help texts. You can switch off the help contents by setting the attribute to false by appending (or prepending) a !, i.e., :!arc42help:.

This question/answer was provided by @ascheman, who also came up with the underlying implementation in the AsciiDoc version of arc42.