I'd downvote but I've come to the understanding that I shouldn't downvote if I disagree, so... Take my upvote, truly an old people trait

It was necessary with typewriters.

Then the earliest word processing programs didn’t do layout well, so the habit made the leap to computers.

Then years later it’s seen as an old person’s habit by people who’ve only ever known systems with smart text layout.

This is the only true OPT in the thread. The rest are middle aged traits at best.

I succumbed to the single-space-after-periods madness a few years ago. I'm used to it now, but the transition was hard.

Two spaces after a period is my eccentricity as a writer.

It's not even legitimately gained by being that old...I had a crush on this science teacher and HE was old enough to use two spaces. So I did. And 20 years later I still haven't shaken it.

The only good thing is that nothing else legitimately uses a double space, so find and replace is quite easy.

I cannot stop myself from adding two spaces!

It has the advantage of distinguishing abbreviations (e.g. "e.g.", "i.e.") from sentence stops, so that's why the GNU coding standards recommend using two spaces in code comments, to allow emacs to be able to properly detect sentences and correctly use commands like (backward-sentence, forward-sentence and kill-sentence)

Computers automatically change it?? I see two spaces here In what you wrote. Typically phone and things like word have settings to show double space after period as single or not and some android keyboard apps auto correct spaces. But I hate single space it makes it hard to read. Punctuation and Capitalization it helps the reader.