Witch Hunter Robin/WMG

Robin is bulimic.
Look at the episode where Robin and Dojimma go undercover as waitresses at Harry's and have to wear fanservicey uniforms. Don't Robin's bones look like they're protruding? (She is seen eating food in a few episodes, which rules out anorexia.)
 * Alternately, she's just skinny. There have to be some naturally skinny people; otherwise, how would anorexics know what to aim for?
 * Naturally skinny people shouldn't have protruding bones.
 * Another guess would be that setting thing on fire takes energy. Lots of energy.
 * Several episodes show Robin being woken up in the middle of the night/very early morning and working to quite late. Her schedule is all messed up, and if she's learned to ignore hunger anyway (fasting, anyone?) it could be that she simply doesn't eat as much as she should.

Robin doesn't need her glasses.
Sure, she's told that the reason her abilities go haywire is short-term myopia; but Robin is rarely shown looking through her glasses when using her powers. It could be that someone in the STN-J just realized that Robin needed something external to boost her self-confidence. Perhaps Amon?
 * Watch the first couple episodes where the glasses are introduced. It shows Robin's POV through the lenses, and the view through the lenses is, in fact, clearer and sharper than the view outside of them. She does need glasses, it's just not a very strong prescription.

The series takes place in the same world as Painkiller Jane.
"Witches" and "Neuros" are different names for the same thing; people with Superpowerful Genetics; many of whom are abusing these powers and bringing down the attention of extra-legal agencies who hunt them. It is commented in WHR that America handles Witches "differently."

The series takes place in the same world as X-Men.
For many of the same reasons as above. "Witches" and "Mutants" seem to have an awful lot in common, and they've both got government agencies plotting their downfall in less-than-ethical ways.

The series takes place in the future of one of the alternate universes Homura created to save Madoka.
In one of the worlds, Walpurgisnacht was defeated, though Madoka still either died or became a witch and was killed. While Homura left for the next world, everyone else in the world got on with their lives. Eventually, some puella magi settled down and had children with civilians. The result was a new breed of "witch" in the form of the descendants of the undead puella magi. "Orbo" is the form of a hybrid Soul Gem/Grief Seed.