Facebook has quietly launched a new feature that lets you translate posts and comments on Facebook pages with the click of a button.
When you see a comment in another language, you should also see a small "Translate" link next to the "Like" and "Share" links. Clicking this will immediately use Bing to translate that post into your native language. You can then hit the link again to change it back. It doesn't work on every comment on the site yet, but it works on many of the non-English comments I tried.
Right now, the feature only works on Facebook pages — not profiles — but chances are, you're more likely to run into comments that need translating on other pages, where you don't know anyone, too. The feature is expected to roll out to Facebook profiles eventually.