Discord is spyware because it collects all information that passes through it's communication platform. As Discord is a centralized communication platform, all communications have to go through official Discord servers, where all of the information can potentially be recorded, and the vast majority of that information has been confirmed to be recorded, such as all communications between users. Discord has also been confirmed to use other spyware features such as various forms of telemetry. Discord's only source of income is from investment, and it has received over $70 million dollars. Discord cannot be built from source and the source code for Discord is unavailible.
Discord does not make it's source code availible
It is impossible to download the Discord source code and compile Discord, which means that it is impossible to prove that Discord is not spyware. Any program which cannot be built from availible source code is potential spyware.
Discord confirms that it collects large amounts of sensitive user data
User's e-mail address
All text messages
All VOIP Data (voice chat)
Open Rates for e-mail sent by the computer