I really hate this kind of "I don't care" logic floating among hackers or even just scientists. If I'm to argue, I'd start by pointing out the amount of space

I really hate this kind of "I don't care" logic floating among hackers or even just scientists. If I'm to argue, I'd start by pointing out the amount of space is not an integer. So arguing 1 or 2 is already wrong. Kerning of the font take cares about the spacing you have there. So the advice of using 1 space is really that it is understood that you have a single space after period, and the designer take that expectation into the kerning decision. The bottom line to me is that if you can't publish a book via a "traditional" publisher using that typographical decision then it is very likely to be wrong. Argue all you want about why you don't care about that. But for many people that reflects on the care/effort you put into your work, and likely I shouldn't care about work like this. The other thing I hate much is the trivialization, which is related to the "I don't care" culture. From my experience, many things are trivial at first glance. But it is likely wrong. Most things are very complicated with a lot of subtleties involved. Seeing them as trivial is often a sign that they really don't understand the subject very well.