
Latrans |

They still seem to think otherwise, based on how they did things in their group or quoting other spell effects that function as such. I mean you play PFS games so I assume you know what you're talking about.
However seems I need to show them otherwise, aside from the "I'm the GM" ruling.
What other spell effects are they quoting? Based solely on the wording of wall of fire I’d say it can hit with pass only once since you aren’t passing through again on you’re turn, you’re exiting the wall.

blahpers |

The spell deals "passing through" damage (2d6 + CL) to creatures that are in the area off effect when the spell is case, per this line:
If you evoke the wall so that it appears where creatures are, each creature takes damage as if passing through the wall.
It does not deal "waves of heat" (2d4 or 1d4) damage to such creatures since the creatures aren't on the correct side of the wall--indeed, they aren't on any side of the wall.
Creatures starting inside the wall do not pass "through" it to exit, as "through" implies passing from one side to the other. So no additional damage for that sort of movement.

Pizza Lord |
Amusingly, this means that someone standing exactly on a wall of fire can simply stand there in the flames until the spell ends without taking additional damage. Welcome to badly-worded spells.
As amusing as it is to think about. I think it falls under the common sense understanding that standing in a fire deals damage. I think they'd have to point out if it didn't work that way, magic effect or not. :p

Latrans |

Amusingly, this means that someone standing exactly on a wall of fire can simply stand there in the flames until the spell ends without taking additional damage. Welcome to badly-worded spells.
It need a “Creatures that end their turn inside the wall take damage as though passing through it.” line added to it.