I also got a google dashboard notification to come join the Flayn kerfuffle, and I find some of the arguments to be rather peculiar.
For some reason people are saying Flayn's fashion sense and conservative nature makes her feel more like a child. I wholeheartedly disagree, and it's odd that people assume less clothes and/or gaudy fashion choices make a character feel more mature.
Flayn's speech pattern is also "mature" to me (outside of the obvious RAWR moments), and I really enjoy speaking with the educated noble characters in general because, well, I like characters who take pride in the fact they learned how to speak eloquently.
All in all, she reads as a 17-19 year old princess/noble character; people just keep projecting anime archetypes onto the cast which is skewing the collective perspective. I have yet to S-support her since Marianne and Catherine come first, but she's always been massively appealing to me - a person who likes nobles.
She's not your 12-year-old fish-loving niece, but the fanbase has decided she is.
