Well, the only (literal) meaning of "know" that doesn't fit what everyone else on this thread was thinking it meant is:
(3) archaic : to have sexual intercourse with
So we should rephrase
"Odds are, one should never trust a programmer who thinks they know [X]. Odds are they only think they know really know [X], but they haven't gone too much farther than figuring out how to use the library."
With something along the lines of
"Odds are, one should never trust a programmer who thinks they have had sex with [X]. Odds are they only think they have had sex with really have had sex with [X], but they haven't gone too much farther than figuring out how to use the library."
(3) archaic : to have sexual intercourse with
So we should rephrase
"Odds are, one should never trust a programmer who thinks they know [X]. Odds are they only think they know really know [X], but they haven't gone too much farther than figuring out how to use the library."
With something along the lines of
"Odds are, one should never trust a programmer who thinks they have had sex with [X]. Odds are they only think they have had sex with really have had sex with [X], but they haven't gone too much farther than figuring out how to use the library."
What is this smut in my Hacker News?
source: http://www.merriam-webster.com/netdict/know
Or perhaps you meant implications of the word "know" in play? (: