Reminder that confirmation bias can be really hard to see around. It’s literally one recommendation. About a submarine. Which you probably didn’t talk about for very long. And is something you can’t buy or have a choice in supporting. Let’s be real, Discord and YT as corporations have little interest in furthering the Military Industrial Complex, and anybody who says otherwise better have solid evidence.
As for the other comment, I don’t see a source that says anything about Discord selling conversational data directly to advertisers. Discord is certainly not a privacy-focused application, but it’s not in their best interest to sell your conversations directly like that.
As for what they put in their TOS, it’s pretty standard fare. Almost all user-generated content services will have clauses like that so that they don’t get sued, because they’re hosting your data. (reminder: this is not legal advice.)
The clearest forms in which you will be advertised to are when you search for products, or visit sites with trackers. But even then, your data isn’t necessarily being sold. Google, for instance, is generally not in the business of selling data to other advertisers, because they themselves are an ad business and having their own data gives them a competitive advantage. I tell you this to help you understand why companies are motivated to track you. Youtube, quite frankly, doesn’t give a crap. For YT ads, expect to receive personalized ads, but for video recommendations, it’s far easier for them to just do it based off of other stuff you’ve watched and what other people are watching. I’d be surprised if their algorithm uses external tracking data, because why would they? They have all they need in-house.
If you and your friend really care about privacy and never want to worry about this again, you’ve got a lot of work to do. Stop using Chrome/chromium/blink/webkit. Use Firefox or one of its more privacy-focused cousins. Disable Javascript on as many sites as possible. Have as few accounts as possible, and delete your Google/AMZN/FB/reddit/YT etc. Use Tor or a VPN to prevent IP-based tracking. Make sure your DNS is 1.1.1.1 or 8.8.8.8, or better yet, AdGuard DNS. And of course, stop using Discord or any cloud-hosted software. Teamspeak, IRC, and Signal/Matrix are good alternatives. Also shoutout to Quassel for a semi self-hosted IRC setup.