I prayed about this, and was asked to post up the log here.

In a nutshell, Wilhelm doesn't understand the word "yes," whether as a say, or a sayto.

Here's the log:
Large Room
This room is dominated by a large table spread with maps. Compasses, pens,
and straight edges are scattered over the maps that the cartographer is
working on. The maps do not look familiar to you. A large map dominates one
wall, it seems to show all of Thera, and more that you did not know was there.
A small cot sits in a corner and in another corner are the stairs down.


( 2) A map of Arkham is here.
( 2) A rolled up map is here.
A rolled up map lies here on the ground.
Wilhelm the gnome mapmaker is here hanging up his latest maps.
A cityguard is strolling through here, keeping the peace.
An adventurer is here, trying to get a party to brave the Feanwyyn Weald.
Wilhelm the mapmaker is muttering to himself as you enter the store.
Wilhelm the mapmaker says 'Where on earth can that deliveryman be? He's never been this late...'

<100%hp|100%ma|94%mv|2500tnl|drunk> give note wilhelm
You give a hastily-scrawled note to Wilhelm the mapmaker.
Wilhelm the mapmaker reads over the note.
Wilhelm the mapmaker says 'Hmm... alright. So you are the substitute on this delivery run. You look sort of young to me, but I suppose that if Simon vouches for you, that's good enough.'
Wilhelm the mapmaker says 'Here. Take these to the Chartmaker in Arkham.'
Wilhelm the mapmaker gives you a bundle of maps.
Wilhelm the mapmaker says 'He's been waiting for these for a while and will be anxious to receive them.'
Wilhelm the mapmaker says 'His store is on Main Street - very easy to find. Still... here. Take this along with you.'
Wilhelm the mapmaker gives you a map of Arkham.
Wilhelm the mapmaker starts to turn away, but then turns back to you with a worried look on his face.
Wilhelm the mapmaker says 'Erm... you *do* know how to get to Arkham, don't you?'

<100%hp|100%ma|94%mv|2500tnl|drunk> sa Yes
You say 'Yes'
Wilhelm the mapmaker says 'It's a simple question, really. No need to make it complicated.'
Wilhelm the mapmaker says 'Do you know how to get to Arkham -- Yes, or No?'

<100%hp|100%ma|94%mv|2500tnl|drunk> sa Yes
You say 'Yes'
Wilhelm the mapmaker says 'It's a simple question, really. No need to make it complicated.'
Wilhelm the mapmaker says 'Do you know how to get to Arkham -- Yes, or No?'

<100%hp|100%ma|100%mv|2500tnl|drunk> sayto wilhelm Yes
You say to Wilhelm the mapmaker 'Yes'
Wilhelm the mapmaker says 'It's a simple question, really. No need to make it complicated.'
Wilhelm the mapmaker says 'Do you know how to get to Arkham -- Yes, or No?'

<100%hp|100%ma|100%mv|2500tnl|drunk> nod
You nod.

<100%hp|100%ma|100%mv|2500tnl|drunk> sa yes
You say 'yes'
Wilhelm the mapmaker says 'It's a simple question, really. No need to make it complicated.'
Wilhelm the mapmaker says 'Do you know how to get to Arkham -- Yes, or No?'

<100%hp|100%ma|100%mv|2500tnl|drunk> pray Newbie quest is broken. Wilhelm doesn't understand "yes."
You pray to the heavens for help!

<100%hp|100%ma|100%mv|2500tnl|tipsy> sa No
You say 'No'
Wilhelm the mapmaker sighs heavily.
Wilhelm the mapmaker says 'And you're the one I'm trusting with my precious maps? Bah.'
Wilhelm the mapmaker shakes his head in dismay.
Wilhelm the mapmaker says 'You just go out the East Gate and follow the Eastern Road until you get to Hamsah Mutazz. Go right through and out the other side, then keep walking until you hit the docks.'
Wilhelm the mapmaker says 'Eventually, you'll reach The Dragon Sea; lots of open sea there. It's across that, a little north of due east. Turn hard'a starboard if you meet the Cliffs of Insanity.'
Wilhelm the mapmaker says 'Coastal town - can't miss it if you see the harbor. All the same, you might need these.'
Wilhelm the mapmaker gives you a map of Western Thera.
Wilhelm the mapmaker gives you a map of Eastern Thera.
Wilhelm the mapmaker gives you a map of Hamsah Mu'tazz.
Wilhelm the mapmaker says 'Now... what else is there that I'm forgetting?'
Wilhelm the mapmaker taps the side of his head in thought.
Wilhelm the mapmaker says 'Aaah yes. You're going to need a boat. Go and see old Nicholas the Boat Seller -- he's in the warehouse on River Road.'
Wilhelm the mapmaker pulls out a scrap of torn parchment and jots a quick note.
Wilhelm the mapmaker gives you a scrap of parchment with a note on it.
Wilhelm the mapmaker says 'If you haven't got enough copper to buy a boat, give that note to Nicholas; it'll get you something, anyway.'
Wilhelm the mapmaker looks at you and says 'Now be off with you! You're late already!'

Emphasis mine:

><100%hp|100%ma|94%mv|2500tnl|drunk> sa Yes
>You say 'Yes'