Ye Olde Inn

How do people handle this? I see two options.
1) No movement on whole pit of chaos squares.
2) No movement on whole and partial pit of chaos squares.

I go for option 2, but also allow movement on partial squares that contain less than half pit.

As I'll build my dungeon 2.5D style, tiles with grids, I will have a rule for such things written down.
It might be: if a figure's base fits completely into the "safe" part of the square, all is fine.
If it doesn't, but there is both a "safe" and an "unsafe" part in the same square, then you roll a die. On a [insert a symbol according to the danger here], you fall into whatever the case may be.
On the original tile, intuitively, I would handle it exactly as you.
I have wondered about that shitty quest book entry...

I'm for no movement on whole Pit of Chaos squares and mostly Pit of Chaos squares. I'd allow movement on partial squares that contain less than half pit. If a square can't be agreed to contain less than half pit, treat it like a special pit trap--rolling a skull means you're now Morcar's boy.

The Pit of Chaos is a pit: ". . . Anyone moving into the pit. . ." Others may not agree, but I'd also allow moving over it:
3) Jump a whole or mostly-pit Pit of Chaos square like a pit trap.

If you wanted a Pit of Chaos in a home-brewed Quest, the EQP provides further rules guidance from a long pit trap:
4) Jump 3 whole or mostly-pit Pit of Chaos squares by rolling a black shield. Jump 2 squares by rolling a white shield.

5) Other tricks to cross Pit of Chaos squares:

• Rabbit Boots from RotWL
• Ice Bridge Spell Scroll from the BQP
• Air Walk potion from the EQP
• Wand of Magic, Wall of Stone, and Pass Through Rock (or Wall of Stone and Elven Cloak of Passage) for an unlikely move across 2 Pit of Chaos squares