Most journals have a peer review process, where there are several rounds of reviews and modifications over a single paper.
In my particular case, one of these reviews was, in my opinion, a bit over the top. In this case, the reviewer asked me to expand a set of equations that are explained in any undergrad numerical analysis book. It even has a very well described Wikipedia page. And the set of equations took an entire page of my paper.
Yet, my PI at the moment told me it was just better to comply and get the paper ready (it had already been accepted subject to these changes).
My new PI told me it seemed wrong to him, since it is a very basic set of equations and the fact that one reviewer is not familiarized with it, is not an excuse to break the rhythm of the paper, since suddenly a whole page of equations can do that for you in a paper.
He told me he would have fought it back.
What is the overall opinion in different fields with respect to this?