Font Book isn't foolproof, but chances are if it says a font is safe to use (or that it has problems), the information is correct.
Font Book abụghị ihe nzuzu, ma ọ nwere ohere, ma ọ bụrụ na ọ na-ekwu na font dị mma iji (ma ọ bụ na o nwere ike inwe nsogbu), ihe ọmụma ahụ dị ka ọ dị mma.