Mojang Studios has announced that increased moderation tools have been added to the Bedrock version of Minecraft. These will allow moderators to permanently ban players who don't follow the game's community guidelines "when sending online messages using our services (Realms) or Featured Servers, and communicating online through signposts and books."
Singleplayer games will not be moderated. The Bedrock version of Minecraft is the 'main' edition, and the Java edition will be unaffected by this change. Minecraft has always had the option to ban players from individual servers: this new option blocks them from the game entirely.
At the moment this does seem like something of a blunt instrument, with the only option being the permaban: "moderators can hand out permanent bans that extend to all versions of Minecraft (except Minecraft Dungeons) in order to target severe offenses, meant to cause harm to others. We are also working on introducing temporary bans for lesser offenses."
Bans will be handed out for violations of Minecraft's community standards, and the examples of behaviour that may receive such a punishment are serious indeed: hate speech; sexual content and grooming; real-life threats; doxxing; linking to malicious software; impersonating developers; cheating; and commercial spamming.
Clearly this new tool is about pursuing genuinely bad people, rather than a moderator banhammering someone they don't like (which does happen). Whether that's the way it will be used, especially in a game that says "bans are permanent, non-negotiable, and cannot be removed by support" remains to be seen.