What determines the questions available for selection in the tour page?

Question

Diamond moderators can edit the new about pages. In the second section from the top—entitled "Ask questions, get answers, no distractions"—that takes us to an opportunity to select one of a page full of questions from the site as the example question used on the about page.

The selections currently available on physics are a little idiosyncratic.

Is there some rhyme or reason to these?

I suppose that we want a good example question to:

• Be accessible to the intended audience (perhaps even to the newest and most naive person in that audience)
• Be judged at least decent by the community (positive score)
• Have more than one answer which are also judged acceptable (again positive score)

What else? How does a question end up on the list?

Answer 1

Apparently the posts have to be short, with at least two short answers (<=400 chars), shouldn't have any crazy formatting, and should be open.

Relevant Data.SE query

An interesting thing to note is that if the question satisfies the above criteria, but the accepted answer doesn't, the system pretends that one of the shorter answers was accepted and puts the green tick on it instead in the about page. (Happens if you try to select this post)

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Actually, this makes the example questions iffy on some sites:

On science sites like Physics, generally meaty, conceptual answers (and well-explained questions) are preferred over terse ones. Which means that most of the answer examples there seem undernourished and not-as-good-as-we'd-like. Not much we can do about that, though.

With Skeptics (See comment above), since posts with "fancy formatting" aren't allowed, there is pretty much nothing left (since they use blockquotes everywhere). Add that to the fact that Skeptics similarly likes long answers, and you're left with one OK-ish post.

Answer 2

To formalize the proper criteria, as per the query linked in the other answer: in order to appear as an eligible choice for the Tour page, a question must:

• Be less than or equal to 400 characters in length, including spaces (the rendered HTML is checked for this criterion, not the Markdown or rich text)
• Not contain any of the following formatting:
  • Bulleted lists
  • Numbered lists
  • Quote markup
  • Spoiler markup
  • Code markup (both inline and block)
  • Images
  • Headings
• Not be community wiki
• Not have been posted by a deleted or nonexistent user
• Not be closed
• Have a score of at least 5
• Have at least two answers that meet the following criteria:
  • Not posted by a deleted or nonexistent user
  • Not community wiki
  • Less than or equal to 400 characters in length (again, checks rendered HTML)
  • Not containing any of the seven formatting types not permitted in questions (see above)
  • Having a score of at least 1
• At least one of the two qualifying answers must have at least one comment

It is possible to flip a switch to disable parts of the criteria on specific sites: this will waive the length and formatting criteria, and maybe some other criteria (I don't know which specific ones). As far as I'm aware, that switch is only flipped on Skeptics.

Additionally, there is a generic "unicorns are eating my daisies" question that appears on sites that haven't selected a question, or that have no eligible questions. As far as I can best tell, if a question selected for the tour later becomes ineligible (e.g. it's edited to become too long or use a forbidden formatting type, the user who wrote it deletes their account, etc.), the system will automatically revert it back to that generic question.