Everyone is right in the sense that throwing a hand grenade kills the intended target as well as others.
Way back in the old Linotype days, and before, each column had a count for letters and punctuation. I’m not going to swear these are accurate, because it’s been years since I’ve done this, but for example: a,e,o,u each counted as 1. An i or a period or an apostrophe counted as 1/2. Some capitals, but not all, counted as 1 1/2. Ms and Ws would count 2.
So, if you had to write a headline for a one-column story, which, for example, had a count of 12 (for a 12 pica width), things were fairly easy. If you were setting type for a headline on a one-column story, you added up the count of the letters and if was 12 or less, it would fit. Assuming the type was 12-point. Of course, if the type was larger, say 24 point, then the width count was half. So you would count up the letters and divide by two. I won’t even go into larger type.
In other words, each column, or combination of columns, had a word count, including punctuation according to the size of the type.
Suffice to say, when writing headlines, you wanted all the space you could get. Since single quotes counted 1/2 rather that 1, the standard became single quotes in headlines, double quotes in body copy.
Although it’s becoming less common, that’s why a comma in a headline actually means “and” except when it doesn’t.
My only cite is I used to do this for a living. I 'm sure I cleared this all up.