I asked a question that was declared a duplicate (Does the Catholic Church teach that only Catholics are Christians?). I want to be a good steward and not leave it to clutter the stack. Is it recommended that questions be deleted by the OP if they are marked duplicate?
Similar question on Meta: Duplicate question etiquette: to delete or not to delete?
In general, duplicate questions are useful because the serve as signposts that point readers to the answer to their questions. It's generally discouraged to delete "good" duplicates, that is, duplicates that use different phrasing to ask the same question as was asked previously.
That said, in this particular case, it may not make too much of a difference. Unanswered questions that have a score of –1 or lower are automatically deleted after 30 days. If its score is zero, then it will survive at least a year. If it has a positive score, then it will never be automatically deleted.
Personally, I'd recommend not deleting the question. That way the community can decide if it's a useful duplicate. If they agree that it is, then it will end up with a positive score and continue to point readers to the original question for years to come. If the community decides it's not useful, then it will be deleted eventually anyway, and won't "clutter the stack" for long.