I would like to suggest a place we could draw the line between Hermeneutics.SE and Christianity.SE.
Before I do let me note that this is a brainstorm idea, not one I'm overly invested in. In fact, I still think having two sites is arbitrary and not a useful distinction. However, that's not my call and if we are going to have two sites to deal with, we might as well define them as clearly as possible so that they both have a shot at being as high quality as they can be. In the end @Richard is right that this will come down to community consensus and that both communities must come to some level of agreement about their respective scopes, however we need to start somewhere and work out the details from there.
I propose that exegesis is in-scope for both sites.
Neither the field of Hermeneutics nor Christianity as a religion are meaningful on their own without the exegesis of texts. No good answers on Christianity.SE should be void of good exegesis that show how a particular doctrine was arrived at and the principles of hermeneutics cannot be applied to a text in any meaningful manner with wandering into the realm of exegesis.
However, Hermeneutics.SE should work forwards from a given text but stop short of application and doctrine...
Questions that start with a word or passage and ask for an analysis of it should be asked on Hermeneutics.SE. "What does word mean in Verse X:Y?" should be approached from a hermeneutical background that examines the text in context. Other verses and texts may be referenced in so far as they aid the understanding of the language and context of a passage, but not specifically to make an extended doctrinal point or provide application not derivable from the passage in question. A textual or hermeneutical relationship between passages should be shown rather than just theological.
Questions about a point of doctrine and what Scriptures support them should be off-topic. "Practical theology" or extended application beyond explaining the text should be discouraged.
...and Christianity.SE should only work backwards from doctrines to their defenses but avoid interpretations of single texts.
Questions that pose an individual point of doctrine or Christian tradition should be asked on Christianity.SE. "What do Christians believe about X?" or "What is the Biblical basis for Y?" should be demonstrated using exegesis of the Bible (or the relevant other sources like Catechisms, Creeds, historical writings, etc). These questions may be best answered by those with a good understanding of hermeneutics, but will be an exercise in knowing relevant passages and how they apply, understanding the theological frameworks of Christianity, etc. Verses used in support of an argument will be used on the basis of their theological relation, not necessarily the properties of the text.
Questions asking only about the meaning of a specific word or verse in a particular context should be off-topic. However, questions asking for the practical application of a verse or passage should be allowed. These would be defended using the text, but inside the bounds of a given theological framework. If needed, a parallel question about any textual issues could be asked on Hermeneutics.SE.
Both sites cover other topics besides the crossover zone at exegesis.
Hermeneutics.SE would be the place to discuss the various hermeneutical methods, deal with textual and historical criticism, and cover historical interpretations as they relate to the understanding of texts, etc.
Christianity.SE would be the place to discuss theological frameworks, points of doctrine, application of Scripture to daily life, the difference between different traditions, historical people and their influence on Christian practice and belief, etc.
This leaves Judaism.SE with a parallel role as Christianity.SE.
Practical application of texts and working backwards to defend doctrine from Scripture using a Jewish theological framework would squarely on topic there. However Jewish scholars offering their understanding of the OT texts under examination in questions here are more than welcome.
