jetpack_seo_custom_title_conflicted_themesCan be used to specify a list of themes that use their own custom title format. If current site is using one of the themes listed as conflicting, Jetpack SEO custom title formats will be disabled.
jetpack_seo_front_page_description_max_lengthCan be used to limit the length of front page meta description.
jetpack_sharing_headline_htmlFilter the sharing buttons’ headline structure.
jetpack_sync_error_idc_validationFilters whether the sync_error_idc option is valid.
jetpack_auth_typeFilter the type of authorization. ‘calypso’ completes authorization on wordpress.com/jetpack/connect while ‘jetpack’ ( or any other value ) completes the authorization at jetpack.wordpress.com.
jetpack_idc_non_admin_contact_admin_textAllows overriding of the default text that is displayed to non-admins prompting them to contact an admin.
jetpack_idc_non_admin_notice_textAllows overriding of the default text that is displayed to non-admin on the Jetpack admin page.
jetpack_idc_unsure_promptAllows overriding of the default text using in the “Unsure what to do?” prompt.
Jetpack Developer Resources 