I've always been of the mind that Salesforce-specific questions need to stay here. Users on CRSE and SO may not be aware of governor limits, Locker API, Salesforce-specific optimizations that may exist, etc.
My litmus test for this is simple: if you remove all of the Salesforce-specific language, does the question become nonsensical or otherwise impossible to answer, or would the answer you would provide change under this condition?
The goal of this test is simple. If you can remove all the stuff that only works in Salesforce, and the answer doesn't change, it is not related to Salesforce technology and doesn't belong here. A "yes" to my test means that the question belongs here--it's Salesforce we support, and this is a Salesforce question.
For example, the first question, you considered it a code review. Aside from the fact that this is Apex, and we likely have the highest percentage of Apex developers across all networks, I would argue that CRSE would likely not have provided the following:
FYI, if you changed it to "before insert" you could avoid the recursive update. – sfdcfox
This little comment directly reduced the CPU time and DML statements used, perhaps significantly, reducing future possible problems and giving that developer's users a better user experience. Can you guarantee the OP would have gotten this on CRSE?
As a general rule, the core developers we have on SFSE are more likely well-equipped to answer a Salesforce question on CRSE, than their developers are well-equipped to fully answer a question here.
Of course, I am aware that some of us also go over to CRSE, but it feels like maybe we're "forced" to go visit CRSE just to make sure that people using Salesforce are getting the best possible code reviews... on a different network? Why not keep them here?
Also, CRSE has a different set of rules. I've tried answering questions over there and mostly just gave up. They are even more unfriendly to outside posters than we have been perceived to be.
I realize that in order to participate in any community, you need to abide by its rules, but they seem content to shoot first and ask questions later (and never explain why). There's a reason why I'm still under 600 rep there, even though I've been on there for ages.
I'm aware that not everyone likes code reviews. Many probably won't do anything different if we suddenly "officially" supported code reviews, except perhaps not flag it in to the dirt before someone who's willing to do such a review can answer.
I'm also not saying that we should support 500+ LoC questions, or deal with more than perhaps 5 different issues in a single piece of code (even on CRSE, you're not likely to see more than 3-5 suggestions in an answer).
However, by answering some code review questions, it may help other visitors that have similar problems with bulkification, optimization, etc. To look at any question and immediately dismiss it as a code review is a wasted opportunity.
I agree that we're not here to do any arbitrary code review. That's what CRSE is for. If you're asking about optimizing a C++ program, SFSE can't help. However, our domain-specific knowledge can, and should, be leveraged to provide support to the Salesforce Ohana, even if that support means doing a code review.