Correcting grammatical errors versus content in post-graduate coursework submissions in the sciences
I am somewhere in between physics and mathematics. My personal policy is this:


I mark any spelling, punctuation, or grammar mistake I find, but I do not explicitly search for them. However, I usually do not go at lengths to explain why something is wrong.
This does not affect the grade unless the number of mistakes severely affects the readability of the text or is particularly egregious. (Being in Germany, I may be more lenient on submissions in German by non-native speakers, depending on the programme’s main language and other factors.)


My rationale for this is:


As I have to thoroughly read the text anyway, the additional effort for marking mistakes are negligible in comparison to the reading time. In most of the cases, it’s adding a comma, crossing out a letter, or replacing a single word. This applies to analogue submissions as well as to digital ones.
Just telling students that they made language mistakes somewhere in their writings does not really help them. The effort of seeking help from a third party is unfeasible in most situations (and disproportionate in comparison to my effort). However, I expect that they are able to find out the source of a specific mistake that I marked.
The admission requirements should not and cannot be so strict that only people who completely mastered the language can be admitted. In many languages, even native speakers tend to commit some systematic spelling mistakes (in particular regarding punctuation) that can only be weeded out this way.


So in short, I think that the other HoD’s rationale is blatantly misjudging factors.

We do not have any departmental policies regarding this here, but I know many that follow a similar policy.