I know this the general HN opinion of free & closed software, but I think this is one scenario where it doesn't ring true. On top of Discord's privacy policy explicitly disallowing/negating data selling, the CEO, CTO and CFO have all made public statements that they have no interest in the monetization of user data. The CTO has suggested that they're at least breaking even with Nitro subscriptions, and they've shrugged off acquisition attempts, instead wishing to go public at some point.
The risk of Discord performing commercial suicide via a data selling scandal appears exceptionally unlikely.