Q:

Is purpose of GIS SE to provide Q&A primarily for end-users of GIS tools?

Question came up because I saw this was labelled as off topic: How to save python Rtree spatial index to file?
I've always thought of GIS.SE as a QA site for everyone working in/with data in a spatial context; developing, scripting, or working with end-user tools that deal with spatial data.
Since Rtree is a core component of dealing with larger spatial datasets (or perhaps more broadly 2-dimensional datasets), I feel like it would fit squarely within GIS.SE's scope.
The closing of that question and some other recent experiences suggest to me that those developing tools or scripting with spatial data ought not use this site but rather Stack Overflow. 
Is it the intent of the moderators to curate GIS.SE specifically for end users of GIS tools, and to push that all other spatial data-related scripting and engineering questions move over to SO? 
If so, where do we draw the line? 
Does interacting with the APIs of other popular Toblerity libraries, like Shapely, constitute SO questions while using ArcPy methods consistute GIS.SE-friendly questions?
Does information architecture as it relates PostGIS spatial data storage belong in SE while higher-level query issues belong in GIS.SE? Or should all be moved to SO?
If someone were developing a module or adding functionality to underlying QGIS features, would those questions belong in SO while only the questions from an end user clicking through the UI workflow belong here on GIS? This question (Where do questions about QGIS plugin development belong?) suggests that it all ought to be here, which furthers the confusion.

A:

Firstly, I'd like to point out that I believe the question to be on topic and I have reopened it. I believe there is often a fine line when it comes to python questions on this site. Sometimes they are definitely within the realm of GIS and sometimes they should be asked on [so]. Sometimes, they would probably work on either site. I think the question you linked to falls in the latter category. 
Next, I think it's worth pointing out that 4 of the 5 votes that closed the question were not moderators. The final vote, which was a moderator, closed it, but that could have been anyone in the community.  As a moderator, I can see that there were two "leave open" votes as well. It's possible that the people who voted to close it weren't aware of the rtree module. Or, maybe, they were looking for something else in the question that was more specifically spatial.
I don't know much about rtree, but from what I can tell, this question is on topic and therefore reopened it.
If someone wants a question re-opened and cannot vote for that then they should comment, edit, upvote, perhaps raise in chat, perhaps write a Meta question, before going to last resort of a moderator flag. 

A:

You summarized your question as:

Is the purpose of this GIS site to provide QA primarily for end-users
  of GIS tools?

Clearly that is not the case because our Tour says:

Geographic Information Systems is a question and answer site for people interested in GIS, Remote Sensing, Photogrammetry, Geodesy and
  Surveying, as well as Programming/Databases specific to the
  aforementioned.

If a question is about spatial programming, and focused, then I think it is on-topic here.
Saving python Rtree spatial index to file? is about Rtree: Spatial indexing for Python and is well-focused so, unless any other answers here convince me otherwise, I would vote to re-open it.
There is an rtree tag (with an excerpt but no wiki) and I also notice that we have many questions involving rtree that are not yet tagged that way.  It would be good to reinforce the on-topicality of rtree to GIS SE by improving that situation.

