We can't close all questions that could feature safek d'oraisa in the answer based on an answer to another question that lays out the rule of safek d'oraisa l'chumra, because there might be an answer to a new question that doesn't deal with safek d'oraisa at all.
@IsaacMoses I'll try to explain it in forthcoming comments; feel free to continue the discussion at your convenience.
Goal #2 is: The same question should not have different answers in different places.
Let's take the tefillin on Chol Hamoed example.
If we have two different questions asking about tefillin on Chol Hamoed, it's possible that one question will contain an answer saying that we do don tefillin on Chol Hamoed, while the other question might have an answer saying that we don't wear tefillin on Chol Hamoed.
This is undesirable because it leaves open the possibility of a reader only seeing one question, and thus only seeing one answer. Such readers might be missing out on pertinent information.
If one of the questions is closed as a duplicate, then there will only be one place to post an answer; thus, if conflicting answers are posted they will be in the same place. Readers will then have access to all the information.
Of course, it is possible that there could be only one question open and the answer might still be lacking some information. But that is simply a case of a non-comprehensive (or wrong) answer, and there's nothing we can do about it except post (or encourage others to post) the missing/correct information.
The above is all in a vacuum (e.g. where the two questions are exactly the same).
But most of the time the two questions are not exactly the same, and therefore Goal #3 becomes a factor as well. As I mentioned in my answer (and I don't know if you agree with me on this point), in my opinion Goal #3 is the most important. Since this is fundamentally a site for asking and answering questions we need to ensure that every question (that is otherwise on-topic, not primarily opinion based, not too broad, etc.) can receive an answer.
So if it comes down to a conflict between Goal #3 and Goal #2, my opinion is to sacrifice Goal #2.
However, as alluded to in one of my above comments, if Goal #2 can be upheld without violating Goal #3 even though it makes it harder to achieve Goal #3, and the alternative is sacrificing Goal #2 entirely, then Goal #2 should be upheld.
Now, to take an example, let's apply this to the rabbit case.
If we close B (rabbits on Tuesdays) as a duplicate of A (rabbits with no qualifiers) Goal #3 is made harder, but it can still be upheld.
If we leave B open we are now subject to the possibility that an answer to B will contradict the answer to A, which violates Goal #2. (Goal #1 would probably also be violated because a good answer to B would probably reproduce much of the answer to A, in order to explain that Tuesdays are an exception rather than the general rule.)
Therefore, upholding Goal #2 (and Goal #1) outweighs making Goal #3 easier, and B gets closed.
However, to take another example, let's say A is "What beracha is made on an apple?" and B is "What beracha is made on an orange?".
Both questions should remain open (in lieu of a third question "What beracha is made on fruits?") because it is possible to answer the question about oranges without addressing apples, and vice versa.
Now in this case, both Goal #2 and Goal # 1 are violated, because it is possible that the answer to apples will be reproduced to oranges (e.g. "the beracha for fruits in general is ha'etz"), and it is possible that the questions might get contradictory answers (e.g. an answer to A says "the beracha for fruits in general is ha'etz" but an answer to B says "the beracha for fruits in general is ha'adama").
But since Goal #3 is more important, we sacrifice Goal #1 and Goal #2 in order to uphold Goal #3.
@IsaacMoses Here's an example (it might not be the best example, but I was more pointing out a theoretical difference rather than one that is likely to occur):
We have the following question:
16
Total
There are 13,550 seifim in Shulchan Aruch.
Breakdown
Orach Chaim — 4,170
Yoreh Deiah — 3,700
Even HaEzer — 1,988
Choshen Mishpat — 3,692
Methodology
I looked at the beginning of every siman where it says how many seifim are in that siman. I input all the data into an Excel sheet and...
My answer there says that there are 13,550 seifim in Shulchan Aruch.
Theoretically I could have had my answer as just one sentence: "There are 13,550 seifim in Shulchan Aruch."
If I wanted to avoid all the downvotes I would probably get on such an answer I might add: "I know this because I counted them."
However, someone might assume that it would be reasonable for a complete answer to this question to provide more details.
Discussion on answer by Alex: Closing…
Discussion on answer by Alex: Closing…