Please consider implementing the use case you are looking for using a LivePage.
This extension is available as a sample project with one work item type: Topic.
To create a discussion thread - create a work item of type 'topic.' To send a reply create a comment. On the project home page you can see how to access and render work item data on the wiki pages.
Work item form is configured to see only relevant information, including also a filtered form that is used when you create new topic.
To be informed when new comment is posted - add yourself as watcher.
Installation
- Review path to svn executables and repository url in install.bat
- Run install.bat - this simply imports the project to the sandbox folder
- Open polarion administration and mark Sandbox/forum as project