The composition of Mark was an interesting question, and I found elements of it would fit nicely on Biblical Hermeneutics, but (despite some interest to the contrary), the Apostolic Fathers texts are generally considered out of scope for Biblical Hermeneutics questions.
Patristic questions tend to fit better on Christianity Stack Exchange, where we have tags for:
- Apostolic Fathers
- Pre-Nicene Fathers
- Early church
A question similar to this one--focused on the history of the text but not explicitly on Papias--could be asked in-scope on Hermeneutics, but if we want to interpret the words of Papias specifically, existing scopes on the sites seem to favor keeping it on Christianity.
My thoughts on where topics would fit best:
- the circumstances prompting the writing = Hermeneutics
- the historiography (narrative strategy and selection of events included) of the writing = probably Hermeneutics
- the rhetorical / compositional techniques = Hermeneutics
- what the early church said about the text = Christianity
(the omniscient narrator question does strike me as more of a Hermeneutics question, unless it's seeking for Christian apologetic responses)
I don't see a tag on Christianity that directly covers the history/composition of Biblical texts--though "manuscript", "authorship, "early church" or the tag for the specific book being evaluated might be relevant. Perhaps an "authorial intent" tag could be created--but I suspect most questions that would fall under that tag would belong on Hermeneutics. Were it not for the focus on the Papias quotation, I would have suggested moving this question to Hermeneutics.