The poem
My father used to say, "Superior people never make long visits, have to be shown Longfellow's grave nor the glass flowers at Harvard. Self reliant like the cat -- that takes its prey to privacy, the mouse's limp tail hanging like a shoelace from its mouth -- they sometimes enjoy solitude, and can be robbed of speech by speech which has delighted them. The deepest feeling always shows itself in silence; not in silence, but restraint." Nor was he insincere in saying, "Make my house your inn." Inns are not residences.

Wonderful, unique poem.
A great poem...I'm researching you in Language and you are a very interesting person!
If her father really said this, then kudo! The wit in this poem is fantastic. Any parent trying to encourage their children to "leave the nest" should remember to call the house an inn. This poem reads like a proverb--wise sayings. It's like taffy--just waiting to be pulled apart and savored.
Lindsey,
Have to be shown Longfellow's grave refers to the fact that a famous author was buried nearby where Marianne Moore grew up and that her father was disgusted by houseguests who would need to be shown around like tourists and not just be able to fend for themselves.
Though Longfellow is buried in the Mount Auburn Cemetery, Cambridge, Middlesex County, Massachusetts, USA, and I have no idea where Marianne Moore's father's "Inn" was - or if she is even the speaker of this poem.