It’s actually just a funny coincidence, though it’s funny when people freak out about it. Mao’s “little red book” is written 红宝书, while the app is 小红书, so the connection is only really there in English. Red is a reference to two institutions the creator was involved with, Stanford Business School and Bain & Company, both of which use red as their main color (I imagine the general association of red with good luck may have factored in as well). As for note vs book, I mean, a notebook is a “little book,” and note is short for notebook (e.g. Death Note).

If you actually look at the app and what gets posted there and what doesn’t, it’s pretty silly to assume it’s a reference. It was originally called “Hong Kong Shopping Guide” and was targeted towards tourists, the userbase skews female and relatively well off. It’s like Instagram, there’s lots of cat posts and the the like, lots of fashion, I’ve come across some pretty impressive furries, and it’s even got a decent sized queer community, particularly popular with lesbians.

Even if it were an intentional reference to Mao’s book, like, so what? The users are the ones putting out content and they’re just regular people. Not everything is some sinister plot.