I've read this question, this question, and this question which all address a similar topic, but I guess I was looking for further clarification. I noticed there aren't any tags like "Overflow". I presume that if someone were to ask a question about how Overflow implements a specific method - say, a 5th order Weighted Essentially Non-Oscillatory (WENO) scheme - it would be on topic. How about if they asked how to enable the scheme in Overflow? Or how that might change other Overflow parameters? Or how that might affect the solution or computational cost?
I think MarkBooth's answer to a related question applies here. To summarize with a quote from his answer:
The criteria on issues like this should always be: Are answers to this question likely to help other people in the future?
If an answer is so localised that it will never be of use to anyone else, then it should be closed as such.
If it is so general that it fits within the remit of Superuser or one of the operating system specific sites (as, I believe, with the R package installation question), then it should be migrated there. If we can't migrate the question for some reason, it should be closed with a suggestion that the other place is more appropriate.
It is the grey area in-between that we should consider appropriate for
As a side comment, if you make an "overflow" tag, you should fill in the tag wiki for it right away so that it's clear that you mean a CFD package. (Maybe "overflow-cfd" would be even better.) Otherwise, I think the tag will lead to confusion.