Anything else
A technique you use that is not in the guide, a board size you wish existed, a rating that felt two levels off, a translation you would like to see. Ideas are read with the same seriousness as bugs, and several of the things on the site started as somebody's one-line email.
What makes a report useful
- The URL, before anything else. It identifies the exact board or page. A puzzle report without one usually cannot be reproduced at all.
- What you saw, and what you expected instead. Two plain sentences are worth more than a paragraph diagnosing the cause — the diagnosis is the easy part from this end.
- Send it while it is still annoying you. A rough note today beats a tidy one next week, and a screenshot beats a description of a screenshot.
What happens after you send it
Puzzle reports go first: the board is pulled out of the pool and replayed against the solver, so those usually come back with a specific answer rather than a thank-you. If the verifier really did let something through, the fix is a code change and a regenerated board, not a quiet deletion — the blog gets a note.
There is no ticket tracker and no auto-reply, so nothing will confirm your mail arrived. Expect a few days. Your address is used to answer you and for nothing else; there is no mailing list to end up on.