Ricardo Zea beat me to it, but I agree, there shouldn’t be any problems in hyphenating a quote of someone else, especially since you can at times make editorial edits to quotes to get the meaning accross (say substituting “him” with [John]). There is one exeption though: if what you’re quoting has a fixed right margin (or left in a rtl setting), ie. you’re quoting a poem, you can’t introduce hyphenation.
I strongly disagree with Kevin Hamilton’s suggestion of turning hyphenation off for large displays. It seems he’s implying that hyphens are less readable when the line length is long, however the real problem is that the meassure (characters per line) is to high. Instead of adding a quick fix and removing the hyphens when the lines are too long, fix the actual problem instead and prevwnt the lines growing too long. Traditionally 50-70ish has been considered a good meassure, there’s no reason the web shouldn’t conform to the same.
When it comes to hyphenation and languages it is true that each language qould need their own dictionary/ruleset. Each language has different typographic and ortographic rules which, among others, define how and when words can be broken to a new line.