I was taught when writing hand at junior school in the 1950s to leave the space of one letter after a full stop, semi-colon, colon, exclamation mark, or question mark.
Half the space of a letter was to be left after a comma and before and after brackets.
When I learnt to type we were taught to leave two spaces after the punctuation marks listed above, except for commas, which merited a half-space.
Some typewriters had no exclamation mark, so you typed a full stop then backed up a half-space and typed an upper case vertical line.
Computer keyboards do not have a half-space, so even if we wanted to the half-space rule would be very awkward to use.
Some time before I sat my Highers in 1967, new rules for punctuation were handed out at school. Actually I think they came in gradually, because we were, aged 10, instructed to write to-day as today and to-morrow as tomorrow and various other words lost their hyphens too.
Later the rule about leaving spaces after stops disappeared, as did the rule that "which" had always to be preceded by a comma and of course, the so-called Oxford comma, which I had been taught (the comma before and) was suddenly a heinous crime.
I still object to seeing sentences like, "the colours in the Union Jack are red, white and blue" because I was taught that the sentence read, "the colours in the Union Jack are red, white, and blue"
Another rule that some publishing houses have done away with is the one I adhere to: that inverted commas around direct speech must be preceded by a comma.
She said, "I love you." Her boyfriend replied, "I love you too. Let's get hitched!"