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Hello!
What she did was more of a mistake than a crime. (McMillan)
I understand the sentence as follows.
What she did was something which belongs to the category of mistakes, and not to that of crime.
The sentence as a whole emphasizes the pettiness of what she did by comparing it with crime.
Thanks in advance
What is the question?
Yes, you're absolutely right in this example, although without context it's impossible to know if in fact what she did was actually legally a crime, and it's just the writer's opinion that it should be deemed simply a mistake.
We use this construction quite frequently to amend the "category" of something:
"I bought a coat the other day. Well, actually, it's more of a jacket than a coat."
"I had a lovely cake for dessert. Well, it was more of a tart than a cake."
***** NOT A TEACHER *****
Good afternoon, Kazuo.
(1) My teachers told me that sometimes it is easier to analyze a
sentence if you fill in the missing words:
What she did was more of a mistake than (it) (was) a crime.
(2) Also, one of my books said that your kind of sentence is
pretty similar to:
What she did was a mistake RATHER THAN a crime.
Have a nice day!