This is related to Should we allow questions about amateur ciphers?, but I'd like to focus on what should be concretely done when one such question surfaces. Should it be:
- Closed only when too unclear (my initial reaction to example 1)?
- Closed on the grounds of the FAQ entry Do we accept questions asking for cryptanalysis of your cipher-hash function design ?
- Closed unless clearly worded and showing some potential?
- Same, but commented with a short refutation (rather than a full answer), and closed?
- Answered by a simple argument, perhaps after re-phrasing (my second move, after example 1 improved to the point I understood it)?
I'm not too keen of (2.), being myself a culprit of something similar. But (5.) and even (4.) come with the risk of attracting more similar questions, and making the site a mix of academic-level and overly trivial stuff.
Edit: some excellent contributors did (5.) for example 2, and managed to inject some wisdom in answers to a rather uninspired proposal. We seem to seldom apply (2.)
Also, perhaps there should be a tag for this kind of question? I have used the existing "classical-cipher" but it is a poor fit. "Home-grown"? "Trivial"?