I think emphasizing words is so primitive idea, that it should have at least some use pretty much regardless of the language. If you want to draw attention to a specific word, shouting it will probably do the trick, more or less. If such idea is not carried in a tradition, I bet people will invent it soon enough. The details may wary, probably. You can say the word in higher tone, slower, louder, syllabes separately stressed ... stuttering? But as far as I can see, that's all empasizing the word by saying it in a way that separates it from the rest and thus draws attention to it.
Dothraki does indeed have some syntactical and semantical (if i use the word right) ways to emphasize words, and perhaps they default to these means sometimes when English would simply stress words. Or maybe it's the other way around. I surely don't know. It's not like English lacks the general options Dothraki has. Eg:
Indeed, that is my hat. (change a word to emphasize it)
That is, yes, my hat. (change word order to emphasize (or de-emphasize) part of sentence)
