Just Post

Just use Find/Replace.

Find (double space) Replace with (single space)

I’m sorry I’m over 40 and was never taught to do that crap.

My 53 year old coworker does it even though it gets marked as an error in Word. I'm 40 and quit years ago when people figured out that fonts no longer require it for there to be obvious separation between sentences. I don't think it's really an age thing so much as it is a sign of adaptability, maybe?

I'm still a couple of years under 40. I only did this when I needed to extend the page count of a paper. However, my old man punctuation thing is that when I use commas before and after I, "quote," something on a sentence. Also, I don't care what Microsoft Word defaults are now, I write in Times New Roman.

I stopped doing this before I turned 40. :P

Over 40. Never do this. The word processor has been doing it for me since WordPerfect 5

I never did that, even on a typewriter. Word processors do a decent enough job of spacing and it’d just look weird online.

Also a lot of people who put a space before punctuation, as in "really ?", which I've been told may be a tell that the writer is french or studied french.

(A lack of capitalization for country/demonym-ish nouns and adjectives may be a tell that the writer is norwegian—we just capitalize the proper country name, the rest comes off as random capitalization we'll often get wrong, with or without autocorrect.)

OP, this is a genuinely sent post on literally the first day of a new year. I want you to ask yourself something:

Does being bothered by this bring you any form of joy or happiness?

Does being bothered by this bring you any form of stress?

If the later is more true than the former, maybe you should think about that. You're taking time out of your day to be stressed about this thing and if isn't even paying you back in any meaningful way. It took you maybe 10min to make this post? Where would you be if that time was spent doing something you actually like doing instead of trying to bend the world on something so inconsequential as extra spaces?

I don't know if you'll take anything away from this, but of everyone stopped being hung up about things that didn't effect us, we'd all be better off.

I do this in formal writing.

I stopped that a long time ago and don't care who continues doing so. However I know that I'm dealing with a person who may be starting to sundown when I get emails written like that.

I get annoyed by trailing spaces for no reason.Trailing paragraphs before a page break are cursed, though.