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The bounty manager does have an email displayed on his profile, so you can always send him your petition there, despite not being able to send him DM on bitcointalk (he may have the ignore DM from Newbies activated, despite many of the posters on the thread being Newbies).
As stated above, if you do not want to keep on performing tasks for the campaign (as you later state), you can simply stop doing them: you’ll have nothing to report and thus nothing to be processed by the campaign manager.