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.
Is Mariemaia really Treize's daughter, or did Dekim lie to her? The question is never given a definitive answer, though the novel and manga hint that she's not, since Dekim's Famous Last Words are "I can make another Mariemaia if need be! After all, I found her on the stree-" However, Mariemaia is definitely Treize's daughter as indicated by Episode Zero in which an injured Treize is cared for by Leia Barton. Whether or not the Maremaia seen in the movie is the real one or not is another matter entirely.
The English dub makes this somewhat more ambiguous, with Dekim saying "We can always create another Mariemaia! I made her, after all!". This could possibly be interpreted as Dekim staking his claim as The Man Behind the Man. Dekim might have used Mariemaia's parentage as a pretext for turning her into a figurehead, but claims that if she were gone, he could do the same thing to any other girl he finds. A bit of a stretch, true, but that's why we have this trope.
Fashion-Victim Villain: It's bad enough that the regular troops of the Mariemaia Army wear pink Nazi-style uniforms. But their "M"-emblem on their service hats make them look like McDonald's employees.
Tear Jerker: Heero's speech to Wufei during the final part of their battle in Endless Waltz really tugs on the heartstrings.