How does Israel decide who gets a visa to Ramallah?

Haaretz's query as to why some visitors receive regular visas, while others receive "Palestinian Authority only" stamps, went unanswered. (...)
The Interior Ministry said it does not have representatives at the Allenby Bridge crossing.
The Israel Airports Authority said, "Israel Airports Authority employees fulfill their function in keeping with directives while maintaining the dignity of the travelers and insuring a proper level of service. The authority supervises the employees by means of a variety of methods. Stamps are given by border supervisors only (who are not authority employees)."
The Negotiation Support Unit, which advises the PLO's Negotiations Affairs Department, prepared an opinion paper on the Israeli visa policy, which was sent to consulates and foreign missions. The opinion stated: "Third states whose nationals are subjected to such illegal policies have an obligation to object once the facts are made known to them and their nationals ask them to respond or to take action. Choosing not to object would imply third states' acceptance of Israel's unlawful acts, in violation of third states' duty of non-recognition [of these acts.]"

fonte Haaretz, Amira Hass, How does Israel decide who gets a visa to Ramallah?