Not true. At the very least it can leak your IP address. There's a reason whatsapp & other messaging services have an internal proxy for generating web previews.
FYI your decryption key can be MITMed during this process by anyone with physical access to the system, which defeats the purpose of encrypting the disk in the first place.
>Doesn't Discord require every user to create a new account, even if they're already using Discord in some other community?
No, the same account is used. You get prompted to choose a nickname each time you join a server though.
>So when they say "a Discord server", they really mean it--they're like droplets running independent deployments or whatever
No, they're probably all run on the same compute. The "official" name for a discord server from the API documentation is actually a "discord guild" and it works pretty much like a subreddit.