Shouldn't these be merged?
I think in principle they have different meanings, though "Church history" is certainly a subset of all history. But if we can't rely on people to know the difference - it's certainly not obvious, when asking a question, that these separate options are available - then we should just merge them.
Our history questions are generally about finding out what happened in the past, and why. It is a bit of a broad tag but it makes sense, in that some questions engage historical scholarship and some don't. For this reason, I argue that the history tag should be retained.
Church history "should" mean the history of the Church as such - with a focus on her institutions, corporate activity, and self-understanding - as opposed to other historical topics, even if they have a Christian slant, like:
- What specific people in the past thought and did.
- How certain historical events (wars, plagues, ...) and conditions (social, economic, ...) affected Christian practice.
- When particular things happened for the first time.
- Whether conjectured events really happened at all.
But this usage may be specialized enough, and the relationship between the two tags so obscure, that we may as well just have "history" and be done with it.
So, I have this philosophy about tags. What they should mean is irrelevant. How the majority of people are going to use them - whether correctly or not - is what matters.
I use a tag to stem the flow of information. If I'm interested in church-history, then, I need to recognize that others are going to probably forget and just use history. So, if I really don't care about bibilical-basis and eschatalogy, I'll ignore those, and maybe favorite 'history' and 'church-history' knowing that the both tags represent the sum of what I need.
As such, I don't see any benefit in separating the two- semantically or logistically.
Therefore I would argue we should just merge the two.