It's just that several typos and the comment being stretched to a single long line made the comment uncomprehensible.
It should be:

<!-- One way of activating the REST services is adding these lines.
     The server is responsible for adding the corresponding servlet automatically.
     The class org.jboss.as.quickstarts.html5rest.HelloWorld  
     has the annotation @Path("/") to receive the REST invocation. -->

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