I follow convention with quotes (SRS) but occasionally I put the (") inside (HuwG) because I get an impression that the quote and my sentence as a whole seem unclear. Some book publishers follow a system with single stroke quotes; I am unsure of their rules.

Some commas are necessary for clarity, others are there because of convention. Style manuals and grammarians now tend to eliminate the unnecessary ones.

Mr and Mrs seem to be common UK usage now, but the Mr.-Mrs. hang on in the U. S. and to some extent in Canada. I agree with Peace that they are unnecessary.

Many publishing houses have strict rules, and some publish their own style manuals. I have one for Harcourt Brace Jov. ("Harbrace College Handbook," which now is almost 30 years old) and others. These crutches are handy but no substitute to a good foundation.
I was an editor for a time with one journal (international) and also had to proof some papers from my company that were being submitted to a couple of American journals. For these, I had to eliminate UK usage. 'Recognise,' 'whilst, 'army are,' 'aluminium,' etc., had to be changed. Both UK and American 'languages' were acceptable to the international journal.

Looking back, it was evident that the writing skills of professional employees of the Company, mostly English Canadian but also Dutch, UK, American, etc., were high. (Careful selection by staff and recruiters?)
Attached to the Library support group was a dragon who read and corrected papers submitted for in-company publication and was a great help when preparing papers for journals. Most of her work consisted of eliminating repetition and fine tuning. I don't recall many complaints about incomprehensibility. Spelling was generally good but some had trouble with words ending in -or and -er or similar small problems.