Why do we allow a question to be marked duplicate when the "duplicate question" is much wider in scope than the original?

Question

So I'm researching the difference between "prefer to do" and "prefer doing", and came across this question which asked about the difference in meaning between those two specific forms. It was locked as a duplicate and linked to this question, which asks about the difference between verb + gerund and verb + infinitive in general.

Now it's certainly a useful reference to know in general what the difference between these two patterns in, but I disagree that this is a duplicate, because this is significantly wider in scope than the original question. The OP arguably wasn't interested in the general difference between the two grammatical structures, but rather in the specific differences in meaning between "prefer to do" and "prefer doing". And indeed, the answers to the duplicate question have nothing to say about this specific difference.

Why this is important: differences in meaning cannot always necessarily be generalised and applied to other situations. In cases like these the distinctions are often subtle, and to most native speakers exactly the same, but there are differences for example between:

"I like playing football"

"I like to play football once a week"

In this case, the specific difference between "like doing" and "like to do" is that "like doing" is used to express enjoyment at the activity, whereas "like to do" is used to express a habit, custom or preference. The second sentence doesn't exclude the possibility that you enjoy football, but the focus is more on the fact that you do it to achieve an end result, whereas the first sentence focuses on your inherent enjoyment of playing football.

So if someone asked about the difference between these two forms (as indeed someone has), it would be entirely inappropriate to redirect them to the "gerunds vs. infinitives" question, as that's far outside the scope of their question. As it happens, the majority of answers to that question in particular attempt to give lists for which verbs can be followed by gerunds and which by infinitives, rather than exploring the general differences in meaning.

So my conclusions are two-fold:

1) In this specific case, I think the "prefer to do" vs. "prefer doing" question should be re-opened, as it is decidedly not a duplicate of the linked question.

2) In the general case, I don't think we should encourage marking questions as duplicates when the "duplicate" question is far wider in scope, and doesn't answer the specific question OP is looking for.

Answer 1

Generally Speaking

While it is possible that this specific case is an exception to the rule, it probably is not unless we are given specific reason to believe it is exceptional.

There are a few things we are trying to do here by closing narrower questions as duplicates of broader ones:

1. If the answers are the same, it helps us get you and other new users to a preexisting collection of answers to the question faster if the same general rules do apply. Collecting as many answers and users as we can into one place, makes it easier for everybody to find all relevant information. In other words, as the help center specifies, "The fundamental goal of closing duplicate questions is to help people find the right answer by getting all of those answers in one place."
2. We aim for our website to be a long term archival work, and duplicate closure helps to maintain our database as such. If we can redirect people to good, pre-existing answers, it gets more views for people who originally answered the question, and encourages us to maintain the original page for anybody who might find it, instead of neglecting it.
3. If questioners believe that their cases are exceptional, it gives them and potentially other viewers the chance to read the existing answers to the older questions, and explain how narrowers case are exceptional and require a different answer.
4. We stop needlessly redundant answers from being submitted to the website and the internet in general.

With all of that in mind, we should only close questions if they are real duplicates. That is to say, we should have reason to believe that the answers to the proposed duplicate suffice to answer your question without much additional effort. In the Long Tail of Wikipedia Programming Questions, Stack Exchange co-founder and C.E.O. Joel Spolsky writes:

It is OK to edit a question to make it more general. With the power of editing comes the power to take someone’s selfish, very specific question, and edit it a little bit until they’re asking the more general question that hundreds of people encounter. For example, if someone asks, “I set up a web server at home but I can’t access it from work,” it’s OK to rewrite the question as, “What things should I check when a web server running at home is not visible on the Internet?

In this case, the abstract principle of each question is practically identical, and we can help more people with a slightly broader question of reasonable scope

If you’re going to close a user’s question as a duplicate, it has to be a real duplicate. For example, if a user asks, “What does the IP address 128.0.1.1/24 mean?” it’s OK to close that as a duplicate of a more general question like “What do IP addresses of the form a.b.c.d/e mean?” But it’s not OK to close it as a duplicate of a twenty-seven page guide to netmasks. That’s the moral equivalent of saying “RTFM.”

In this case there are many principles to consider and it may be too difficult to locate and identify which portion is relevant to the question.

Regarding points 4 and 5 in my aforementioned list, how frustrating would it be if somebody prematurely wrote a generalized answer submitted to a specific case in which which it did not apply? It is better to have the question put on hold until the precise need for it becomes evident for that reason. If you or somebody else can explain how your question is distinct from its potential duplicates, then we will consider reopening it. This is what I did when I asked Should "Why can we use inadequate but not 'inspecific'?" be reopened? The original question was closed as a duplicate question suggesting that in- is used to negate words of latin origin, whereas un- is used for germanic derived words, implying that inspecific is germanic, even though both specific and adequate are latin in origin.

Also keep in mind that, if nobody among the question's viewers can spot the difference between your newer question and the older one to make a detailed case for it being reopened like that, then we might not even know how to help you any better anyway. Please keep in mind that unless a moderator is involved, it takes a consensus of five people who have earned the privilege to close a question, so nearly half a dozen people eyes evaluate most duplicates.

A narrower question being closed as a duplicate of a broader question is, by definition a category 3 borderline duplicate, which relies on community discretion to decide if and when they should be closed.

Regarding This Case

In this case, I agree that the supposed duplicate is not really duplicate of its linked question. The linked question is a question regarding when each construction is syntactically permissible, whereas the supposed duplicate inquires about semantic question. Even if there was no difference between the meaning of each forms, which does not seem to be the case by the way, that is the principle which should be explained, and not when each form may be used. There are many questions regarding gerunds and infinitives, so a hasty generalization may have been made by accident.

However, the supposed duplicate does seem to be a duplicate of the other question you provided: “I like to do (be) something” vs “I like doing (being) something” and other questions seem to be of a similar nature too. In this case, we should probably reopen the question to mark it as a duplicate of that, unless or until somebody has a specific reason to object, or a better duplicate can be found.