Reddit is up around 1000% from the recent IPO. Every quarterly earnings call has been a blowout, and they're still just around double the valuation of Pinterest so they're not exactly standing among giants.

Users are valuable, that was sort of the big story of the 2010s...

Data is valuable too, and Reddit has reams of data for targeted advertisements. The entire structure of their site basically makes it the perfect ad machine. It's literally a web of people's interests and hobbies. The data is also valuable for AI.

I guess you mean, how does Reddit make enough money to justify being publically traded? All I can guess is advertising.