TL;DR Discord loves to present itself as a company run by a few gamers just like you. The service aggressively advertises itself as "for gamers" with the hope that this "reputation" alone will propel Discord to the top. This has worked really well. The Discord team has refused, however, on multiple occasions to take certain steps to protect their userbase, described in more detail above such as adoption of E2E encryption or going open source. Instead, the Discord team states clearly in their privacy policy that they will gladly hoard a plethora of data about their users indefinitely, loosely claiming to only delete it when its no longer needed. The data they collect and store includes (but is not limited to) full chat logs, all chat media, a list of who you chat with, email address, IP address, device ID, behavioral analysis, activity tracking on the service, pulling info from social media accounts you link, and much more as stated above and in their Privacy Policy. Discord shares this same data with all of its partners, affiliates, agents, and "Related Companies" while lazily instructing you to check their privacy policy to find out what happened to your information, as its no longer any concern to Discord. In addition, Discord goes further to say "Developers using our SDK or API will have access to their end users’ information, including message content, message metadata, and voice metadata". Their very vague "information" wording allows Discord to send whatever they please while, of course, leaving it up to you to go check their privacy policy and figure out just where and to who Discord sloppily throws your data around. Discord continues to show little to no progress or effort in considering open source code, strong end-to-end encryption adoption, or even something as simple as allowing the deletion of an old account. It is important to note that while Discord allows the "deactivation" of an account, their support team will happily inform you that they do not delete your data and your account cannot be deleted. This data is again stored for an indefinite period of time.
Discord is proprietary spyware. Using it means endorsing and legitimizing it.
Discord relies on its reputation to lure its victims. Despite just starting out as a way for 
to mingle in chatrooms and VoIP rooms, Discord has now expanded to any sort of purpose, even extending to schools where students will use Discord for clubs as well as online projects where communication is done over the platform.
The reliance on Discord is dangerous. Any thing you type or do in this program is recorded for the highest bidder (that be your government or private data brokers). The interface and UX is designed to keep you in the app for as long as possible.
There's no way to "smartly" or "responsibly" use Discord. One way or another, Discord will extract value from you. It's not just about you, but about everyone who uses the platform.
Solutions
There are no "alternatives" to Discord. I'm not going to try to fool you by saying there's a magic bullet to defeat Discord's presence in western society (other than socialism and 
). But that doesn't mean there aren't ways to help.
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Matrix: A decentralized messaging protocol. It supports video conferencing on its main instance as well as support for the Discord "Server" functionality. Easiest solution for a drop-in replacement.
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IRC: The one that came before Discord, community networks can be used if you need to communicate and is just as secure as Discord (public chat rooms with zero end-to-end encryption besides TLS)
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GNU Jami: If there was a magic bullet, this would be it. Completely decentralized, peer-to-peer messaging network that is device based. It is a GNU package, possibly the most guarantee for freedom you can get in this world. The team is small, but if you need somewhere to host your leftist activities that will require more than a court order (or a simple bribe) to de-anonymize by state and non-state (those funded by other states) actors then this is it.
Conclusion
This is a post for self crit. If the service is free of charge, then you're the product. Any leftist should take steps to eliminate their dependency on Discord and proprietary messaging programs. Also any leftist should spread this message and inform others about the risks of using proprietary software.
We should also take Discord as a lesson in how to identify the dangers of proprietary programs and why it could make us vulnerable to abuse (which as we know in a capitalist society, is coming one way or the other). Discord isn't the lone offender, but an example of how nonfree software will always pose a threat to a free and democratic society and only benefits the bourgeoisie.
Let this be the last thing I have to say about this accursed program
Literally have to do this shit all the time. Like one of my employers uses Apple iMessage and I have an android so I can't actually send them important pictures so I asked them if they had Signal, they said no. So now I have to figure out how to get this person to actually download and use Signal because I don't want to admit defeat and use Whatsapp.
Exactly, is is incredibly difficult to get people to do minor changes with communication apps
I wasn't under the impression that it would be easy. But the selfish and liberal thing to do would be to give up.
The thing that keeps me going is the fact that there is no limit to the level of cruelty that proprietary software can bring (nor any limit that people can endure). If I stop, I'm betraying my own beliefs and thus become a hypocrite.
It's not good but it's not that bad. Pick your battles and trying to convince someone to change communication apps is more often than not a waste of time that could be better spent elsewhere.
Virtually all the people I talk to outside of nerdy online tech spaces have even a passing idea of what software freedom even means, most have no idea that they actually have basic human rights to computing. People on this very thread have mentioned how they depend on Discord for social interaction and how they cannot give it up (an idea that disturbs me greatly). The American tech field has dominated the entire world in every part of the supply chain and have historically never shown any restraint (the ROC literally partly exists because of how proprietary and secretive chip manufacturing is made by the US), why would it be different for the digital jails they build and export to the rest of the world.
At the end of the day, it is capitalism that makes the abuse limitless and uncontrollable. If it's not that bad today what will it be like tomorrow?
Raw freedom for it's own sake has no value. Proprietary software doesn't cause much material harm on it's own. Sure manufacturing and outreach cause points of strife for states but the lack of software freedom does not cause material harm.
Surveillance by corporations is more often than not unnoticeable and doesn't affect you that much. The house metaphor doesn't really apply here because surveillance with no action does not effect behavior or conditions whatsoever. Look at China's monitoring of the internet. It's not bad because monitoring on it's own doesn't effect or harm people, it's when the state or capital uses the information to suppress dissent when surveillance becomes problematic. For the vast majority of people, Discord's willingness to give the state apparatus information is a non issue as most content on Discord is not sensitive (if you're using it right), and Discord doesn't fine tune the service to be more addictive like other companies do. Secondly, reliability issues and right to repair are not the same thing as free software. Many physical goods with no electronic components fall victim to this (namely clothing). Making disposable items is a better business model than making reliable and that's why planned obselecne exists. Not because of proprietary software.