jetpack_publicize_global_connections_capFilter the capability to change global Publicize connection options. All users with this cap can un-globalize all other global connections, and globalize any of their own Globalized connections cannot be unselected by users without this capability when publishing.
wpas_default_suffixFilter the message appended to the Publicize custom message.
wpas_default_prefixFilter the message prepended to the Publicize custom message.
wpas_default_messageFilter the default Publicize message.
wpcom_markdown_transform_postFilter the content to be run through Markdown, after it was transformed by Markdown.
wpcom_markdown_transform_preFilter the content to be run through Markdown, before it’s transformed by Markdown.
content_save_preThis filter is already documented in core/wp-includes/default-filters.php
wpcom_untransformed_contentFilter the original post content passed to Markdown.
easy_markdown_support_urlFilter the Markdown support URL.
subscribe_field_idFilter the subscription form’s ID prefix.
Jetpack Developer Resources 