The primary criteria are clarity, objectiveness, and usefulness to others. Questions should be clear in meaning and should lend themselves to being answered objectively. No question is too trivial or too "noobish" as long as it adheres to these guidelines. We strive to support all paper-focused Q&A which benefits the accessibility and efficiency of scholarly research, and in this effort encourage users to the greatest extent possible, to ask objective questions (i.e. questions that have objectively correct answers). The exact guidelines are the product of ongoing community effort. For more information, or to contribute to these guidelines, see meta.aboutpapers.com.
E.g.
We seek to serve anyone who has an objective question about a research paper, whether that person be a scholar, professional, student, journalist, or any other person seeking truth.
No. We simply seek to supplement it. Our current system of peer review is far from perfect and after passing peer review, publications are typically never edited or updated again. Mistakes, confusing wording, and inappropriately used statistical methodology are commonplace in scholarly publications. This is what we seek to alleviate.