Star Trek: 12 Biggest Ever Retcons
10. Ponn Farr's Secrecy
Amok Time was a landmark episode, famous for delving into the Vulcans' mysterious culture. The focal point of the episode is the Ponn Farr, the Vulcans' seven-year mating cycle. Spock is very clear that Ponn Farr is seldom discussed among themselves and practically never mentioned to outsiders (except for "the very few who have been involved").
We see a reversal of this policy of secrecy in The Cloud Minders as Spock openly discusses Ponn Farr with Droxine, the daughter of the High Advisor of Stratos. Why Spock is sharing such a personal matter with a woman he literally just met is never quite explained and is a jarring disconnect from what was previously established.