There's a constant flow of misinformation regarding some Slack that may or may not exists (many are not sure) and is a super secret squirrel club homebase. Supposedly, everything that's decided on Hive goes on there. And probably some things that aren't decided but who knows.
This is all false. This is not how Hive communication works.
Causes and Background of the Myth
Before Hive became its own chain, Steemit Inc ran a Slack channel. All invites needed Ned's approval and everything that was said there had to be kept top secret. Steemit Inc held this Slack and access to it over the heads of many investors, users, project owners, witnesses, and virtually everyone else.
It actively perpetuated this idea that:
- access to the Slack gave one legitimacy
- access to the Slack was the only way to communicate with large stakeholders
- access to the Slack was a privilege and without it no project could succeed
- if someone said something in Slack about your project, that was "the community" speaking
In short, it was about privileged access but the reigns of that privilege were held by the same company that later orchestrated a 51% attack on the very public blockchain it vowed to support.
People in Steemit's Slack had to always offer positive constructive criticism and nothing negative was to ever be said. It was a good Slack for endlessly politely debating in circles. I was personally invited by Ned and then banned by him for getting an invite for my partner. I was reinstated much later on.
The problem with that Slack is that it always had that air of "if you're not a member then you're project is worthless" around it. There was no layered solution to communication - just the Slack. And that started the legend and the artificially amplified status of the Mythical Slack.
Hive Communication
There are three distinct and equal targeted areas of group communication for Hive that I am in the position to speak for and will cover in this post. These targeted areas run in parallel to myriad other Hive chats and platforms.
Hive Discord
The 'main' Hive discord is meant to be a point of information and discussion for virtually everyone on Hive. Since Discord can hold the largest amount of people, this is a significant server with many rooms, channels and active users. It is actively used by project developers to ask questions, by content creators to chat with each other, and by anyone and everyone. Many witnesses, large stakeholders and core developers are active there and make a point to make themselves accessible. The main usergroup colors work like this: red are those who organize and always keep abreast of all developments, yellow are the information points who can answer most questions, green are all the different developers in the ecosystem. The Discord is also bridged with https://openhive.chat (which shares the above description save for usergroups).
Hive Slack
The Slack was put in place after coworking and collaboration among Hive development contributors and witnesses became impossible in Telegram. It is meant to be used to facilitate work on Hive and Hive alone. It is not used for personal projects or general interest topics. This Slack is a "free" version, meaning it has a 10,000 message limit before auto-deleting. Due to this, it must be kept on topic, although people do like to partake in idle chatter. It is assumed and expected that everyone there is working on Hive. Its commonly used to discuss exchange listings, outreach topics, various projects, some anti-abuse, status updates and similar.
Hive Mattermost
Due to the fact that Slack auto-deletes messages, all core blockchain and critical infrastructure discussion was moved to a self-hosted Mattermost. This chat is 99% development talk and most of you would find it about as interesting as watching mold grow. Mattermost is kept very professional and succinct to allow people to have focused discussions on technical topics. Due to the fact that security-related topics come up, confidentiality is important. Virtually everything discussed there you can see on the Hive repository, found here: https://gitlab.syncad.com/hive and can also be heard/followed up in the 
Operation of Chats
The Hive chats are freedom of speech chats. We don't force polite speech on people. We don't tell people what they can or can't say. We don't make people communicate in various unnatural ways. People like to go off-topic during quiet times but when push comes to shove, the purpose is for everyone to focus and work on Hive. Many users do not overlap between the topical chats, particularly if they are busy developers.
Topics Not Covered in Chats
Topics around the promotion or lobbying for voting, either for posts, for witnesses, or for DHF proposals are not part of any of the chats. Lobbying is highly discouraged because the best place for it is on chain.
"Leaks"
There are technically no leaks because the chats are not meant to be super secret. That being said, sharing quotes and screenshots is discouraged because it takes the statement out of context. We have had an incident in the past where a quote was maliciously shared in order to trigger a response in another person. The sharer specifically selected something negative but omitted many positive messages that followed. Such cases are regarded as a matter of integrity.
Teamworking
The purpose of the chats, as already mentioned, is to facilitate decentralized teamworking and collaboration. Communication for such an expansive ecosystem is always a challenge. The three chats augment the set of communication tools that Hive contributors have created and maintain. They are not thee chats but are just chats.
Administration of Chats
I am the creator of the above chats. That being said, I am not a sole operator. I have a partner operator on both Slack and Mattermost (different people). On Discord, unfortunately, there is only one owner possible.
The Discord chat is a free-for-all. Invites to Slack and Mattermost are requested and granted on a need basis. The by-invite chats are, as aforementioned, for coworking and collaboration purposes. They are not for anyone's entertainment, random browsing, personal promotion or anything of the sort. We treat everyone equally, irrespective if they're in the rooms or not.
Removal or temporary separation of users is a very hard decision to make but it does have to be made. I have volunteered to take on this role (no, I am far from being the sole decision-maker). It's very difficult, it's not fun, and I wouldn't wish this on my worst enemy. But ultimately it is likely myself who is pushing the button because for every tool, there has to be an operator. I'm not a large stakeholder and I'm not hiding the fact that I'm in this role. Every time I act must be in the interest of Hive as a whole.
Can these chats be better? Of course. Everything can always be improved upon. Nothing human-made exists in this world that cannot be made better.
There are also many other chats that are part of the Hive ecosystem. It would be impossible and unfair for me to try to list them all here, but perhaps readers can link or describe them in comments below.