In my humble, Microsoft-watching opinion, Discord makes a lot more sense for Microsoft to buy than TikTok or Pinterest, two other "communities" the company was eyeing as a way to grow its consumer footprint. Gaming is Microsoft's most successful consumer space. Users already are able to link their Xbox accounts to Discord.
Microsoft already has Skype and Teams for voice, video and text chatting -- services that Discord also provides. And Microsoft's last foray into growing a gaming community via its Mixer game-streaming acquisition, didn't end so well. But it still feels like the potential synergies outweigh the negatives.
If Microsoft follows its established playbook, it will allow Discord to run mostly independently, as it has done with LinkedIn and GitHub. Little would likely change for people who use Discord to chat while gaming and/or as a gathering place to socialize in various channels -- at least in the short term. Discord is said to run its services on Google Cloud, but a move to Azure would likely take quite a while (if LinkedIn is any indication).