Staff means you work for the company. If you go to a movie theatre and want to find the bathroom, you'd ask the staff (i.e. employees). There's no particular context to staff that doesn't also come with "employees." It's neutral, unexceptional, and it's agnostic to one's place in the hierarchy (the theatre owner and the ticket attendant are both staff).
So to me, it makes sense to place it below senior. Staff is a neutral modifier which does not imply a set level of experience (both trainee and veteran are staff). Senior is a modifier which does imply experience. Junior implies a lack of experience. So, staff would logically fit between junior and senior.
I don't see how your second paragraph follows from the first. Everyone works for the company, from the most entry level all the way up to the CEO and is thus "staff", and there is thus no indication in that sense of the word as to what its level is. So in a title it must mean something different than just "works for the company".
> Everyone works for the company, from the most entry level all the way up to the CEO and is thus "staff", and there is thus no indication in that sense of the word as to what its level is.
Absolutely. It has no bearing on seniority, and because of that I'd assume a neutral level of seniority.
>So in a title it must mean something different than just "works for the company".
I mean, that's what this whole discussion is about. In the context of the English language, this is a rather new usage of the word, and I'm trying to illuminate how its use is changing. I totally accept and appreciate that language is constantly evolving — I'm not sticking up a fuss and calling this wrong — but I'm trying to answer the question of what the word implies.
As mentioned elsewhere in this thread, this largely seems to be initiated by the "Staff Engineer" book[0], and I take at least part of his marketing is creatively "misusing" a word, or redefining a word, in order to distinguish his brand.
No I don't think it's the book / site at all, this title as "one above senior" predates the book by a very long time; I've been looking at job postings and it is pervasive and not at companies that just started using it that way within the last couple years.
The "it's a neutral word so it should be a neutral level" idea is clever but I don't think that's where this word usage comes from. I think it seems like it might have something in common with titles in media companies. What is a "staff writer"? Is that a fairly senior position? I dunno.
So to me, it makes sense to place it below senior. Staff is a neutral modifier which does not imply a set level of experience (both trainee and veteran are staff). Senior is a modifier which does imply experience. Junior implies a lack of experience. So, staff would logically fit between junior and senior.