With her typical irony and wit in place, Marianne Moore's poem, "Silence" is not all about silence, but about both restraint and subtle self-assertion.  These are best expressed through Moore's use of dashes and quotation marks.  The quotation marks, placed as they are exert both an aesthetic choice and an ambiguity that gives rise to multiple meanings.  For one thing, there is an uncertainty as to whether the poet endorses the words in quotations or whether the speaker does.  For instance, the reader does not know how to interpret the words of the father that are enclosed in quotations marks since his expansive sentence is in opposition to the point of his talk.  Thus, the quotation marks seem to enclose words that mock the father. Or, they may indicate the daughter's mocking of the patriarchal authority; at the very least they may indicate the daughter's speech anxiety in the form of her not speaking.  Certainly, it can be said that there is, ironically, both self-effacement and self-assertion. 

Indeed, it is the punctuation that suggests the changes from these two emotions.  For instance, in the lines

...The deepest feeling always shows itself in silence;

not in silence, but restraint."

there is an apparent contradiction with the words, but one that is understandable with the semicolon indicating a significant pause while the phrase "not in silence" indicates the switching to self-assertion that comes with "but restraint." 

Restraint, moderation, discipline, and control are also very characteristic of Marianne Moore's poety.