I'm not sure I agree with giving the green light to what you've posted:
IMO posts that don't reflect the high quality of the site, [...], should be kicked off the list
\$\therefore\$ HNQ should only contain high quality questions.
You have also said 'poor' and 'grey' post shouldn't be on the HNQ.
we want to use the HNQ to drive traffic, yes, but not at the cost of examplifying poor questions
[...]
a number of gray-area posts have made it to the HNQ before, and more will likely happen again in the future.
This leaves me to question what you think should be on the HNQ.
Below is my understanding of the quality spectrum of questions:
- High quality question.
One that has little to no problems. (I.E. Good description, well defined code)
- Medium quality question.
One that has some problems. (I.E. Good description, but we don't have the entire context surrounding the code)
- Low quality question.
One that has a lot of problems. (I.E. Poor/no description, code is missing context.)
Below is my understanding of the 'topic' spectrum of questions:
- On-topic.
One that is undoubtedly not off-topic.
- Grey question.
One that may or may not be on-topic depending on how flexible you wish to be with the close reasons.
- Off-topic question.
One that isn't on-topic on Code Review.
You've explicitly mentioned 'grey', 'poor' (low quality) and 'high quality' questions. But I'm not sure I understand what you want to remove and don't want to remove.
If a grey high-quality question were posted, Function to print command-line usage for a program meta, and we start a discussion saying it's grey should it be on or off the HNQ?
If an on-topic medium-quality question were posted1 should that be allowed on the HNQ? (What you've said I interpret to mean no it should not.)
I think off-topic and low quality questions should be removed from the HNQ bar. This is as promoting these actively harm the site.
Since medium quality questions are the norm, I think, promoting these won't harm the site. And so what is the reasoning for removing these?
This will mean people post more medium quality questions. However we can improve the quality of these independently from HNQ. Some questions can be fixed by editing the question to improve wording, other questions you can comment requesting the missing information.
And so I think improving the average of the site is how to fix this.
A question being on-topic doesn't say anything about whether the question should or shouldn't be on the HNQ bar. As the question could be low or high quality.
It's hard to say whether a grey question being in the HNQ is unquestionably bad for the site.