(and how often do you need to be reminded that nit-picking is hyphenated?)
As a proof reader myself, I think you''ll find it's one word, no space, no hyphenation....
OEDDefinition of nitpicking in English:
noun
nitpicking[MASS NOUN] informal
Fussy or pedantic fault-finding:
nitpicking over tiny details
[AS MODIFIER]: a nitpicking legalistic exercise