There is no point comparing Scrivener with Word, or even Apple Pages. Microsoft is big enough and wealthy enough to have their own engineers write their own text engine for Word, and I haven’t used Word since Apple launched OS-X around 2002 and I could no longer use Word 5.1.a, so I have no idea what happens in recent versions. Similarly Apple Pages doesn’t use the Apple text engine either, but Apple have created another proprietary engine to use in Pages.
The point is, if this is a bug, it is Apple’s bug not Scrivener’s as Scrivener uses the Apple text engine, and other apps which use the Apple Text Engine ought to exhibit the same behaviour. Now, I can’t test using Korean, but I do use Chinese; however, as a native English speaker, my system language is British English and the default language in Scrivener is English. I have my keyboard set up with the menu and shortcuts to switch between English and Simplified Chinese. My default text style is EBGaramond — I loathe Times New Roman
— and when I switch to typing Chinese, the font switches to Songti SC I think but without showing it in the Font button, using Chinese punctuation, and when I switch back to English, it goes back to EBGaramond with proper Roman punctuation including apostrophes. The only time it doesn’t do it is if I move the cursor within the Chinese and then to the end of that stretch before switching to English. It then remains in the Chinese font, but uses the Roman characters within that but Chinese punctuation.
That said, I have just made a quick test in TextEdit — which is the comparison one should make — and typing Chinese and then switching to English without switching to a proper Roman font now seems to access the Roman punctuation, rather than the Chinese punctuation … suspension points are in the Chinese position though. On the other hand, the Roman characters in Songti SC, particularly the ‘a’ are awful, and generally badly kerned.
In conclusion, it seems that Apple may have made adjustments in the El Capitan version of TextEdit, or may have fixed the punctuation access in their Chinese fonts. It seems they haven’t done it in Apple Myungjo though.
Another difference on my machine is that up until El Capitan, I used a third party Chinese text entry system, which sadly seems to be buggy under El Capitan so I’ve switched to the Apple text entry system, which has been improved apparently. That too might be making the difference with accessing the correct punctuation codes.
So, I’d check against TextEdit, and also look into the text entry system you are using for Korean. In the meantime, perhaps Keith or someone on the team will take note of this and investigate at a deeper level, whether there have been changes to the text engine which are not yet reflected in Scrivener, though I imagine that that is unlikely.
Mr X
PS I am merely a long time, happy user of Scrivener, but one who uses it in English and Chinese, but am not part of the team.