These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Alternate Character Interpretation: The final volume gives a far more positive perspective to the Mad Scientist Xombul who was the Big Bad of the earliest stories. He is literally the only person in Galaxity who understands what Valerian and Laureline have gone through on their adventures, and their final encounter is a friendly one.
Fridge Logic: in "Sur Les Frontieres", rogue Earthling Jal rapes Kistna, a member of an alien race endowed with almost god-like powers... which she doesn't use to defend herself.
This may have something to do with the fact that he had lured her out of her armour. While Jal later uses those powers without one, he seems to be burning them out. It's possible that the suit held some significance in the use of the psychic powers that Kistna was blessed with.
Seasonal Rot: At some point after "The Rage of Hypsis" the series starts getting worse and worse. Valérian & Laureline has always had it's share of political commentary and satire, but by the 1990s they have pretty much taken over the series. Instead of portraying cool and otherworldly aliens liked it used to do (remember, this is a series that actually produced its own bestiary), Mézières and Christin start making them into thinly veiled humans. For example, in the last few books we get to see alien gangsters who dress up like Mafiosos and speak Italian, an octopus creature who inexplicably wears a British gentleman's suit, and even a space alien version of Corto Maltese! What's worse, Christin seems to have lost his capability of writing coherently: the plots of the last few albums mostly just have various things happening in succession with little overall rhyme or reason. On top of that, Mézières' art gets more and more cartoonish towards the end of the series. He's still able to draw breathtaking cosmic visions if he wants to (the Wolochs, for example), but many of the supporting alien characters have turned into caricatures of their former selves.
Interestingly, "The Rage of Hypsis" was the last story originally serialised in Pilote magazine, where the series got its start in 1967. Correlation?