My thought with Discord and being acquired by other major companies is I think Facebook would have shut it down or attempted to turn Facebook Messenger into it or something. I don't think they have a good track record of being able to maintain various products.
Google, I think, would have likely tried to change the hell out of it and shut it down within two years. They aren't good at managing products, shut them down all the time, and use everything to take as much ad data as possible.
Amazon is one I just feel would have been a company that would attempt to tie it into Amazon Marketplace and turn it into some sort of Prime/Twitch exclusive thing.
Apple is horrible for consumer access. They might be okay managing it, but they'd lock it down and make it impossible for people without Apple devices to use. They can't even manage to figure out how to allow a news subscription work without having an iPhone.
Microsoft is hellbent on building 'communities' and I think they've shown good management with Minecraft and GitHub in particular, and even Skype (which is more than 10x larger than it was when they bought it, even if it's not the market leader now). They are buying game studios and trying to leave them alone to do what they do best. They want to be the platform that other platforms build on, and I think that would have been a good spot for Discord to be in.