How does one express in writing long, drawn-out speech in languages which use a pictographic orthography, such as Chinese? For example, how would one write, “Nooooooooooooo!”? Do they just repeat the character for “No” over and over again? Do they repeat the exclamation marks? Is there some special symbol they use, like a dash at the end of the word?
In Manga, they write it in really big characters, very often outline instead of solid.
You can use exclamation points or bold or italicize or underline. Punctuation’s pretty much the same.
Manga?
I suppose you do it the same way as in any other language, e.g. Mao screamed, “No!”
OK, but how about for non-screaming but still drawn-out speech? For example, a pleasantly surprised “Oooooooh!” or a smarmy “Yeeeeeeeeesssss?”
Yes, but presumably like English, boldface and italics indicate emphasis in general, but not length in particular. There is a difference between barking “No!” and wailing “Noooooooooo!” which, at least in English, cannot be marked by the font weight or style alone.
I’ve seen a line used in Chinese comics. Something like:
“No-------”
(Except a solid line instead of a bunch of dashes.)
I’ve actually asked this question here before and didn’t get a definitive answer. In writing online, I think that “~~~~~~” is often used to indicate that a word is drawn out.
Just when I need my LaoFuZi comics…you can have the same character repeated several times in a gradually smaller progression, exclamation points, even nonsensical “fake” characters, etc.
From a Chinese friend:
•s, of course, is a character I don’t have installed, but you get the idea… 
I don’t recall such a character.
Let me rephrase that. There is a Chinese character that allows a writer to show the previous character is repeated, exactly once. The reason for that is probably to save time in case the first character is very complicated, but it is never used in a case like this to show emotions.
Emphasis in written Japanese is indicated by the use of katakana.