I would like to find out how common it is to use redaction software, vs. the old-fashioned magic marker. How can I formulate an acceptable question about this?
Reference question that was closed: How common is electronic redaction?
I've been trying to figure out an easy way to look at a question and determine whether it's on-topic or not, in the simplest sense - whether it's a question about law. And I think I may have the beginnings of a good solution, which coincidentally answers your question.
I think that, if you can remove the legal element(s) of a question and it isn't still substantially the same question, you may want to consider whether it is actually on topic here. This is something I've been considering for a while, and perhaps this theory has gaps, but for most questions, this is probably true.
For example, your question asks how common a practice of - let's call it "manual" - redaction is, and you offer a somewhat legal prologue to this, being that the documents that were so redacted were obtained under an FOIA request.
But... would it really be a different question without that first paragraph? I would say not.
On the other hand, many (and I would hope most, if not all) of the questions on our site are defined because of their legal elements, and would be fundamentally different questions if you tried to divorce those legal elements from those questions.
As I say though, it's just the beginnings of a nugget of an idea.
But in answer to your question: I don't think asking how common a particular method of redaction is, on its own, would ever be an on-topic question.
Perhaps if you located some legislation that stipulated how that information must be redacted, in particular applications, or in specific industries, it might be something that could be answered legally.
A question about how frequently people engage in some practice is clearly not a question about law. I even question whether a question of the form "how often does the law require X" is really about law as opposed to politics, since unless the answer is along the lines of "Only in these 3 cases is that (not) required", the question ultimately comes down to asking for a list of political decisions: that is, it doesn't tell you anything about The Law. And it is almost certainly not an answerable question, assuming that the topic has not been professionally researched. For example, a question like "how often do municipalities establish 'by permit only' parking zones?" cannot reasonably be answered, and instead you'll get an anecdote "In my town, they do" or "In my town, they don't".