Only because Western-centric systems don't handle non-LTR text properly.

https://atadistance.net/2019/10/20/japanese-text-layout-for-...

> Baseline font metrics will never deliver great CJK typography because there are too many limitations. > > This is why InDesign J implements virtual body metrics based on Adobe proprietary table information for true high-end Japanese layout. There is no virtual body standard digital font metric standard so everybody implements the missing stuff on the fly and everybody does it different. Unfortunately the irony of it all is that Adobe played a huge role in how these limitations played out in the evolution of digital fonts, desktop publishing (DTP) and the situation we have today.

I have a Kobo reader which supports both ePub 2 and ePub 3, and IIRC you need ePub 3 in order to get proper RTL/top-to-bottom text and Japanese typesetting, as well as proper comics support (if you buy an ePub 3 manga, it'll properly flip the page turn direction and the progress bar; a CBZ or other format won't). But most other readers I run into don't understand ePub 3 properly.

I'm probably lower-intermediate at Japanese, so take this with a grain of salt.

I find that reading vertical text feels better, even though I first learned to read horizontal text. I don't know if this is all in my mind, or it really does have some appeal to it, though.

I’m not native, but have read and spoken Japanese fluently for almost twenty years. I still can’t get used to and hate vertical text.

Maybe it’s because 99% of my Japanese context is business-related or on devices (computer, phone) and I don’t read novels, manga, etc.

Ah, yeah, my main motivation is reading light novels, and I've actually read a few really easy ones. I've also read manga, but it's hard to find any that I like that are also at my level.

I'm not sure how I'd feel if the vast majority of my usage had been horizontal instead.

A typical eye is stronger at up-down motion and weaker at left-right motion. That comes up sometimes when adding rules (guidelines) to tables.

I own a bunch of novels in Japanese, and every single one is vertically-written. Same with all the comic books I own. I think maybe a couple children's manga I had years ago were horizontally-written, but we're talking something I haven't laid eyes on in decades, so I might be mis-remembering.

If you want to try a horizontal text layout novel for some reason, "私小説―from left to right" is one. It's a deliberate choice because it's a semi autobiographical novel about the author's life as a bilingual Japanese and English speaker growing up in the US. The text is peppered with English words and fragments of dialogue to try to convey some of the bilingual experience.

That is the only one I've encountered though.

Mangas often mix and match, depenfong on what best fits the image.

If it's not done a lot on the web, I blame CSS. With horizontal text you scroll the page from top to bottom, with vertical text from right to left. Most HTML/CSS seems to be optimized for the former. E.g. vertical percentage margins don't work like horizontal ones, and CSS3 columns have similar issues.

Definitely

Novels are often written vertically as well, so it's fairly common still.