@user1271772 I don't have as much of a problem with people giving more than one answer, and earning the corresponding rep from them, if they are well researched. The question does seem a bit open ended, but I would say we should see how it goes and correct any "rep hunting" rather than avoid the question do to the possibility of it.

@Tyberius About the first part: I worry that with some questions, we could literally have one person just answering their own question 15 times. Since self answers are not automatically converted to community wiki, this could even be 15 self-answers, which looks quite strange to me. In the past, people who have double answered questions on this site, didn't give substantially long or detailed answers for either answer and it looks a bit "cheap", which makes the site look a bit cheap.

I worry about what type of message that sends to other users who come here and want to quickly gain rep, they could just ask a question and then self-answer it 17 times (for all 17 constraints of the SCAN functional, for example), and I just have a negative feeling about it in general. In any case, I agree with you that we can make a question like this work on the site if we're careful.

If it gets asked tomorrow, I suppose you and I could write good quality answers to set an example for others. One of us could write that CCSD is size-consistent and size-extensive and give a proof for it, and the other could possible write why CISD is not size-consistent and size-extensive and give a proof for that claim. I actually don't know the proof for CCSD off hand,

but I could write quite a lot about CI being size-inconsistent and it's implications for variations of it such as FCIQMC, SHCI, CIPSI, and other types of "selected CI" which give FCI-quality results without including every single determinant.

@user1271772 What if I ask a new question with the "one-topic-per-answer" tag and constrain the number of methods? (because I was only interested in the most generally used methods, not esoteric methods such as OOMP2 or MR-CC etc.). I did not mean to ask an open-ended question.