Ana Marie Cox hasn't read Sotomayor's writing, but accuses her of “not performing at grade level”

Ana Marie Cox, in today's washingtonpost.com discussion:

Successful judges tend to be good speakers and even better writers (Scalia probably writes the most entertaining decisions of the SCOTUS, tho Roberts is also good); Sotomayor's “Latina line” makes me think she's not performing at grade level on either.

Wow, that's a pretty harsh assessment. How did Ana Marie Cox reach her conclusion that Sonia Sotomayor's writing isn't at the “grade level” of a successful judge? Not by reading Sotomayor's writing:

That said: Like 99% of the people weighing in on her nom, I haven't read her all of stuff! Or most! Or any!

What “grade level” does suggesting someone's writing is subpar without actually, you know, reading it qualify you for? Third?