Who is responsible for writing the user story?
Is there the concept of technical writer?
If the story were to meet the INVEST criteria (independent, negotiable, valuable, estimable, small, testable) who on the Scrum Team may need to be involved in doing this successfully?
Given the history of where user stories came from I don't believe they were intended to be highly technical documents but a placeholder for a conversation in which more detail can be derived. This does not mean the team cannot create technical documents if serves a purpose for them.
For the most part, I have seen the product owner create user stories and as the DEVOPS teams discover more they begin to write some of their own stories to support the business case/user story.
Is there the concept of technical writer?
I’d suggest that there may be the concept of technical writing, for which the Development Team role would be responsible in order to create a “Done” increment. One or more team members might therefore need to demonstrate these skills.
For me, since User Stories aren't included in the Scrum Guide, I assume the process governing them is unique to each implementation. Scrum provides us the opportunity to improve our processes.
That said, I'll share what's been working for my teams. It's less about who and more about how. The quality of the story writing is based on how the Dev team understands "Done". We've used that as the starting point.
Since the Dev team works the stories, they are the most critical of how they're written. Once it's become clear what the appropriate quality expectations are between the Dev team and PO, either side can write stories as they need them.
Consistency was the goal; now it's become a part of the prioritization process.
When we get external requests, the same filter is applied. We don't expect others to write stories to match our expectations. As the PO prioritizes the backlog, they should be capable of detecting when a story isn't up to par. They will reach out with questions and clarify the intent of their request as needed so they can best sustain being customer proxy for the Dev team and appropriately prioritize the work.
Ultimately the PO is accountable for the backlog prioritization and the Dev team is accountable for what they've build, but the Scrum Team is accountable for their ability to predictably deliver outcomes matching intent/expectations of the users.
It depends on how you perceive "Technical Writers". I had an experience where technical writers were more proficient in creating stories than business analysts.