I was looking through the implementation of clojure.pprint.* and found that it still uses the old-style metadata to mark vars as private - ^{:private true} instead of ^:private.
I have migrated the metadata to the new style in the attached trivial patch, which can be used in case this is deemed to be an issue.
FWIW, there are some other namespaces which use the old-style metadata as well; I am willing to fix those as well.