Can I make it reply only in certain languages?

Yes. By default we reply to every comment in its own language, but you can narrow that per page:

• Languages to process — open a page's Settings and pick only the languages you want handled (for example, English only). Comments in other languages are left alone.
• Reply language — pin a single language if you'd rather every reply go out in one, no matter the comment's language.

Need something more specific — like "skip all non-English comments on this one ad account"? Contact support and we'll apply a custom filter for you.