I think some of those complaints reaching the front page of reddit may have helped spur this into action by the Chrome team.
Backspace to go back, OTOH, I was aware of, but I doubt I ever wanted. Alt-Left is easier to use because it's less modal. Still bothers me in general when devs screw with established defaults.
I do find the spacebar behavior isn't super predictable when I am trying to pause things, such as youtube .
I've never managed to consistently replicate it by having had the player in/out of focus already, not/scrolled, etc. odd.
EDIT: and before anyone points out that if I'm already using extensions I could easily add another, yes and I would if I had to, but it's not ideal, because 1. Extensions crash, fail to load, or aren't allowed by internal browser pages, and 2. You sometimes have to use other peoples' machines and it's annoying when basic functionality is locked away.
I've never actually seen someone complain about it until now.
Frankly, I would be perfectly happy if space to page went away entirely. I exclusively use two finger dragging on laptops and scroll wheels on desktops to browse websites. I never use space to move down a whole page at a time, and that's a jarring action anyway because it inevitably causes me to lose the context of where I was reading in the document in a way that smooth scrolling accomplished through other means does not.
I don't have a scroll wheel or a touch screen.
The gaming instance is a failure of Web controls to adequately adapt to context. I can see how that would be distracting. I am not willing to sacrifice my space-to-scroll capabilities on that account.
As with Fitts' law, the spacebar is a very large target. Easy to hit. Frequent action. Well-placed use.
You do raise one other point: scrolling tends to make re-aquiring reading point difficult. That's a fair gripe and one that annoys me.
I'm particularly sensitive to it in DuckDuckGo, which smooth-scrolls a pre-set amount in the SERP when scrolling (I forget if by up/down, pgup/pgdwn, space, or other). I absolutely cannot figure out where I was and where I want to be, and have reported this multiple times.
For long-form text, I've taken a strong preferene, in portrait display devices (my tablet when reading) to fully paginated text, and a page flip mode. Much as PDF is an abysmal format in many ways, I find the capability to retain a spatial memory of where content is on a book or in a page is useful, and generally prefer this to smooth-scrolling.
Pocket, which offers a page-flip mode, makes it both brittle and of limited utility. Any up-down motion whilst flipping a page "breaks" page-flip mode and returns to scroll.
Page-flip doesn't clearly indicate location within the work as a whole (Pocket also mutes the scrollbar indicator generally).
And lastly, the pages aren't consistently presented -- effectivly Pocket repaginates a document whenever and wherever you enter into Page Flip mode. I'd prefer it had a sense of what the pagination breaks were for a given viewport size and font selection, and stuck to that.
Or I could read a book....
> I don't have a scroll wheel or a touch screen.
I use the middle button + trackpoint for scrolling - works great. That's the default on most Linux distros/desktop environments, might require some configuration on Windows.
Fitts' Law.
I don't find it jarring at all to read that way, because I know where to resume reading after hitting space. There is one exception: a lot of websites with absolutely-positioned headers scroll incorrectly when you hit space, such that the point you would resume reading at ends up behind the header, and you have to scroll up a bit to reveal it.
A few websites with headers get it right, and your resume point is below the header after hitting space. This makes me much less sympathetic to the websites that screw it up.
I do use paginated reading on my Kindle, which always gets it right. It doesn't quite work properly on the web often enough though.
It's a race to the bottom.
Thankfully on OSX/Safari, this legacy behavior/cruft is not present.
Also, Lazarus is an old plugin for Firefox that saves forms between sessions/refreshes. Too bad goog want to capture new users at any expense. If it doesn't work because the latest hotness is js forms that's a problem with webdevs.