"Is there a meaningful reason, or is it just 'people are pretty much terrible and sometimes specific bits of terrible become cultural habit'?"

"They look very different from us. The Thindar thought they were animals and hunted them." His tone is very very emotionless.

"What?"

"The Thindar thought that they were animals, and hunted them. For sport. Kept their heads on the walls."

"...What do they actually look like...?"

"About this tall, bearded, humanoid - but that's scarcely the point, when you meet something you've never seen before we have osanwë you can check."

"I have no words."

"The Dwarves are a touch wary of outsiders."

"I can imagine. If your brother's married to one will the fact that I'm on good terms with you guys help at all?"

"I am hesitant to send you with my recommendation, I haven't known you long enough. You can mention that we found you charming."

"Fair enough."

"And show them the plastics."

"That I can do."

"Have a nice trip." He turns back to his work.

This is entirely predictable if you know things about this man's personality!

She flies.

To the place where she was told there are Dwarves.

Yep. Hm, there don't seem to be visible cities or anything around, how odd.

There is a road, paved and well-maintained.

Might as well follow it, then.

It passes a very neat, very metal, very closed door in the rock.

That sure is a door. Probably no one is going to be offended if she knocks on it, she would have been warned, right?

The door opens. The people at the door are armed, and bearded, and short, but they do not look necessarily unfriendly. "Hello."

"Hello. My name is Odette Zavier. I came to this world by accident from a completely different universe and have a kind of magic presumably unfamiliar to anyone in this one who I or my sister haven't already told which has many useful properties including preventing people of dying of old age." Her claim of unusual magic may be supported by the fact that she is, as usual, hovering a little ways off the ground.

"Okay. Are you trading with someone in particular or just offering to trade in general?"

"...The latter, I suppose. I am very much in favor of people in general not dying of old age--or other reasons, for that matter--and am interested in distributing both de-aging directly and the mechanism by which it's done."