I cannot comment on RAF Chivenor as I did not have the pleasure of serving there.
However, pointing out the importance of grammar and correct spelling does have some value, especially to the young. If nothing else, it demonstrates that such things do matter to some people, potential employers for example.
I say this, having had a number of years teaching technical subjects.
Eg: graduating students completing questionnaire about the 2 year technical program they have finished. One (of the better ones) shouts out to his fellow students " how do you spell 'red'? Me: (not supposed to be present, but trying to expedite said survey so they don't waste valuable class time) " What do you mean Trevor, what are you trying to say?" Student replies " I want to say 'they (College) should get 'red' of the English course".
Sums things up nicely for me.
BTW I always say I was in the 'are ay eff", as opposed to the 'rafff'. I assume that is the preferred pronunciation.