Today I came across the "Get help with editing" button on the beta cluster. It reminds me very much of the Article feedback project that started in 2010. The placement of the button, the form that opens, the call to action – all this is very close especially to version 5 of the ArticleFeedback prototypes which also gave visitors a form to post something.
I was very closely involved in the ArticleFeedback project in 2013 (as a volunteer). I even tried to convince the German community to keep it. We did in-depth research and number crunching in addition to what the Wikimedia staff did. What we found was not enough to convince anybody: The vast majority of the posts (something like 80%) was not actionable. The same time the number of incoming posts (the prominent placement of the button made it very easy to submit anything) was so high, the small group of users trying to be helpful and act on the posts could not keep up.
We tried to improve the call to action, but it didn't change anything. It was like visitors don't read the call to action, or don't care. They found an input field, possibly confused it with social media, and posted whatever they had in mind that moment: Questions that are already answered in the article, for example. Many just expressed what they liked, or more often did not liked. The most demotivating posts demanded changes to be made.
Keep in mind: Both the failed "post feedback" feature as well as the "ask a question" feature we are talking about now rely entirely on the motivation of a small group of volunteers. If I would need to summarize what keeps a volunteer motivated, I would say: Either if something is fun, or if it creates value the user can see and enjoy.
I'm wondering if the team currently working on the "help desk" project is aware of the pretty large collection of ArticleFeedback documents, and was able to incorporate the main learnings from back then? Personally, I wish you all the best. But from experience I know it's very hard, if not impossible to make something that's more like running a support hotline a fun thing to do, or at least something that feels like it creates value.
There was also a very similar Teahouse project in 2014, lead by Wikimedia Deutschland. It also implemented a button that was visible on every page, opened a small form, and let visitors create new sections on a regular wiki talk page. It failed for essentially the same reasons.