Interesting discussion here. I try to remember that conventions change over time, but I am conservative by nature and it takes work to adapt to changes.
The one-space vs. two-spaces issue after a full stop is by no means standardized anywhere in the world. Both standards have co-existed for a long time, and there is no point casting stones at people who use the standard you don’t approve of. Insisting that the standard is and has always been the way one happens to be used to is just foolish.
It bugs me that today, when we are all pressed for time but have computers that can now do a lot of nifty things that couldn’t be done in the past, the compromises that were adopted when programs and the hardware were less sophisticated are now tending to become standard. There is no reason why we can’t have the superscripts and subscripts and curlicues that typesetters used to employ back in the days when they were a lot more difficult to employ (except the laziness of programmers who don’t want to make it possible). I mean, for example, that it’s a shame we have to write H2O inline instead of having the 2 as a subscript. And the common programming standard of using an asterisk (*) in place of the standard multiplication signs (· or ×) is creeping into common typography, even though the Unicode standard makes the standard signs available. It’s a real shame.
Interestingly for English usage, America and Britain have each retained certain older usages but innovated elsewhere. The Americans retain the subjunctive and use it more often ("If I were king, . . . "), but the subjunctive has largely disappeared in British usage. Britons have by and large adopted the custom of omitting the period after abbreviations that end with the final letter of the word (Mr and Mrs, for example), and retaining it for other abbreviations. (I prefer the American custom, simply because then I don’t have to stop and think about it.) Britons generally and some Americans prefer to write their lists by omitting a comma before the “and” (a, b, c and d); whereas Americans generally and some Britons prefer what has come to be called the “Oxford” comma (a, b, c, and d). I have seen some very sharp debates about which style is clearer; it can, however, be argued both ways.
A good resource to read is Fowler’s Modern English Usage, in the first edition if you can find it, but the second edition (edited by Sir Ernest Gowers) is also very good. But Fowler, the principal—and principled—editor of the OED, had some surprising takes on various issues. (For example, he was a proponent of the simpler spellings, adopted in America, for words such as “program” and “honor;” he felt they were closer to the original Latin than the Frenchified spellings “programme” and “honour.” For the same reason, he preferred the spelling “-ize” as being closer to Greek than the French “-ise.”)