The personality trait that would make Dickon feel at home at Buckingham Palace or at the bottom of a coal mine is that he is very likable.
It is mention trough the book that he has a strange ability to captivate everyone human or not since his ability also applies to animals, everywhere Dickon goes everyone just fell under his spell and find him lovable. We can see the quotation that says :
There really was a sort of Magic about Dickon, as Mary always privately believed. When Mr. Roach heard his name he smiled quite leniently.
“He’d be at home in Buckingham Palace or at the bottom of a coal mine,” he said. “And yet it’s not impudence, either. He’s just fine, is that lad.”
Explanation:
Fang and Max are partners who frequently confide in each other and have each other's back Fang shows an understanding of Max's personality and when upset she often confides in him and he can calm her down their later relationships later develop into love .
<em><u>maybe </u></em><em><u>this </u></em><em><u>was </u></em><em><u>ur </u></em><em><u>answer </u></em><em><u>or </u></em><em><u>it </u></em><em><u>might</u></em><em><u> </u></em><em><u>be </u></em><em><u>wrong </u></em><em><u>too</u></em>
I'm guessing the word that is italicized capacious because in this case it is synonymous with vast, meaning that he has a developed mind with broad views.