Due to her power of resurrection and ability to control fire, Mokou is often depicted as having the same powers as the mythical phoenix (She even has spell cards called "Possessed By Phoenix" and "Immortal Flying Bird Phoenix"), even occasionally generating what appears to be a phoenix-shaped aura. Fans like to depict this as "wings of fire", but in canon, she only controls the flames of the phoenix in her spells. The phoenix is probably more of an aura depicting her immortality.
Fandom is divided as to whether or not Mokou actually is possessed by a phoenix; it would seem redundant, as she is already immortal (unless she did it to grow more powerful).
Mokou is one of the few people in all of Gensokyo to wear pants. This, along with her somewhat forceful way of speaking, often leads to her being depicted as something of a tomboy (perhaps why her parents kept her out of public view). However, because conditions in Gensokyo still resemble those of feudal Japan, pants are hard to come by and must be made by a skilled tailor or imported from the outside world, and presumably are much more expensive than skirts. This may make pants a status symbol, and given Mokou's status as a daughter of the old Japanese aristocracy and her rugged lifestyle, it is likely it would be only natural for her to insist on wearing them.
Fan works occasionally depict Mokou smoking because of her mentioning cigarettes in Bohemian Archive in Japanese Red.
Due to her spellcard "Fujiyama Volcano" and her ability to manipulate fire, a few fans call her "Fujiyama no Mokou."
It is speculated that even Flandre Scarlet's ability to "Destroy Anything and Everything" is unable to kill Mokou, as her immortality effectively removes the concept of her non-existence impossible. And some fandoms make Flandre nervous around Mokou as hers is an existence she cannot comprehend, since she can't see the Eye to destroy. Sometimes fandom pairs Flandre with Mokou as she would be the only one that could control Flandre if she were to go on a rampage and kill people without the risk of being killed herself..