See following test, there is a simple comment line after @modules (and with a blank comment line in between).
Test is not selected by jtreg.

An empty comment line won't be identified as the end of tag @modules, all strings after @modules and before the next tag starts (comment line begin with @ ) will be taken as the value of modules. This makes confusion.

Test example:

/*
 * @test
 * @modules java.base
 *
 * comment without at tag blabla
 */
public class Test {
    public static void main(String... args) {
        System.out.println("JavaBaseTest");
    }
}


Tested with jtreg4.2 promoted b02, b03, jtreg4.2 b03 nightly.

jtreg/bin/jtreg -jdk:/path/images/jdk /path/dev/jdk/test/Test.java
Test results: no tests selected
Report written to /Users/admin/OpenJDK/JTreport/html/report.html
Results written to /Users/admin/OpenJDK/JTwork