I completely agree. I have run things through grammarly, rejected the American spelling on account that I am English, and ignored suggestions to put commas where they don't fit. Then I have submitted the piece to a publication and lo and behold, all those exact changes are made that I specifically rejected. I realise that grammarly is a useful tool but if someone has uniformly used the "non-American" version of spelling then perhaps there is a reason. And at least read the sentence to check that adding the comma actually makes sense.