Is it permissible to face the grave when supplicating for its occupant?

A distinction must be made between two matters: The first is intentionally turning towards the grave and facing it in supplication, seeking blessings or believing in a quicker answer. This is an innovation (bid'ah) and an exaggeration that may lead to shirk (associating partners with God). The Sunnah is to face the qiblah when supplicating, not the grave. As for the second matter, it is supplicating for the deceased and seeking forgiveness for them when visiting their grave. There is no harm in this, whether the supplicant faces the qiblah or the grave, because the Prophet (peace be upon him) supplicated for the deceased at the grave without stipulating facing the qiblah.