At the good article and featured article review processes, reviewers often generate a list of problems that they wish to see fixed. Ideally the editors who are working on the article then fix those problems, but sometimes the review becomes a fix loop. There are two kinds of fix loop: the most common looks like this:

  1. The review lists problems with the article.
  2. The editor working on the article fixes the issues and asks the reviewer to support promotion.
  3. The reviewer reads the article again, and finds additional issues.
  4. The editor fixes the issues and asks for support again.
  5. ...and so on.

The second kind of fix loop is slightly different:

  1. The review lists problems with the article.
  2. The editor working on the article fixes the issues and asks the reviewer to support promotion.
  3. The reviewer does not feel the problem is successfully fixed, and provides additional feedback.
  4. The editor makes another attempt to fix the issue, and asks for support again.
  5. ...and so on.

Cases arise where a nominator doesn't have the expertise to resolve a problem, and the result is that the reviewer must either provide enough detail for the nominator to do the work by proxy, or else stop responding on the nomination page and simply oppose the nomination without giving further details. The first option is fine if the reviewer wants to put in the work, though it would be better for the efficiency of GAN and FAC if that work could be done before nomination. The second option is frustrating for the nominator because it leaves them with no clear path to improving the article.

There is a requirement that reviewers provide actionable reasons for opposes, and this means that most (but not all) fix loops relate to the article prose, rather than other criteria such as comprehensiveness or neutrality. Prose opposes often cite individual sentences, but there are broader reasons for opposing on prose. Essays such as WP:RECEPTION provide help in special cases, and a reviewer can simply cite the essay without giving more details, but in most cases a reviewer has no choice but to oppose on some version of "It's not well-written", if they don't wish to give details because they wish to avoid a fix loop. In many cases I suspect reviewers will skip reviewing an article that they might oppose, because they know they may get sucked into a fix loop.

There's no good solution to this problem. Not every nominator has the command of English necessary to write FA-quality or even GA-quality prose, and it is almost a guarantee that such nominators will not recognize that that's the case, and will be unable to tell whether an article is ready to be nominated. What each reviewer does is up to them, but it should be acceptable behaviour at FAC to oppose on prose and not be expected to give more than one or two examples, and not be expected to return and reread the article or provide a second round of examples.