I occasionally see reasonable questions get deleted by their authors after being closed as duplicates. Here's one recent example:
It seems to me that this undermines the value of the close-as-duplicate system; having linked questions makes finding good answers here easier - and probably via google too.
Is this a situation in which voting to undelete the question is acceptable and a good idea? I'm aware of the conditions in which we can, but I've not seen much advice about when we should.
I'm also aware that authors cannot delete their question if it
- has an answer with upvotes (even if that answer has a net zero or negative score)
- has an accepted answer
- has multiple answers (even if there are no upvotes)
- has an answer with an awarded bounty
- has at least one other question that is marked as a duplicate of your question