Aha! The fix is simple. You just need to use an AsciiDoc line comment for the tag line.
[source,asciidoc]
----
some text
== Introduction
// tag::PQMP-RG1[]
text comes here
// end::PQMP-RG1[]
----
It doesn't matter what comes before the tag::[] and end::[] directives. You always want to prefix with the line syntax for the language in which you are using it. In this case, the language is AsciiDoc, so you use the double forward slash.
Cheers,
-Dan