Is raising a finger to seek permission from the Imam during the Friday sermon exclusive to the Companions, or is it still permissible?

It is permissible for someone who has a valid excuse for missing Jumu'ah to leave the mosque without the Imam's permission, but it is recommended to seek permission. The early Muslims (Salaf) used to ask the Imam for permission to leave for an excuse during Jumu'ah, but seeking permission is recommended, not obligatory. It has been reported that the Companions used to ask the Prophet, peace and blessings be upon him, for permission to leave for an excuse, while the hypocrites would stealthily slip away with him.