right now in the iOS app if you setup an instance I do not see a way to setup another one and seeing as how the current architecture of the product is, I would need multiple servers for my org's needs. the app should be able to handle it as well.

Implement off-the-record messaging (https://otr.cypherpunks.ca/)

Sometimes one's wondering if a post has already been read by other users. I could image that a member list of the channel pops up when one is selecting the read status from the particular post menu ("[..]").
In private chats, a sinple check sign (similar to whatsapp) could signalize if a message had beend read by your counterpart.

Add feature to make video/audio calls (personal/group)

Sometimes a user posts his message in the wrong channel. Deleting the message and repost is a simple solution. However, sometimes the message already contains replies. Is it possible (to make) to move a message including its replies to another channel?

Creating and participating in Polls would be great,
to be embedded within a message.
Like in Doodle, Facebook or Threema:

Option | User1 | User2 | ...

Coke | x | |
Sprite | x | x |
...

OR

Option | Votes

Coke | 3/15 Users
Sprite | 2/15 Users
...

For IT policy compliance, offer the ability to invite non-team members users to Mattermost as "single-channel guests" to have access to read and write to one channel and direct message any other users in that channel.

Potential scenarios include opening discussions with non-team members, including customers, vendors, partners and interview candidates.

Slack offers a very cool possibility: you can ask the bot to remind you of a message after some time.

This is extremely useful when you post a message which requires some reaction by some other users - if (unfortunately) no reaction comes, it is very easy to forget about the question, which will not happen if you set a reminder!

That would be a very nice feature to add to mattermost

This feature proposal is for the ability to encrypt posts/direct messages in the database, with a server-side encryption of the database contents.

Add cusom user groups for mentions. Something like @developers or @frontend to mention all members of group in this channel. Also it would be useful for large teams, when novices does not know who is who - with this feature they can determinate at least group

As a user, I would like to be able to ignore the postings from other users. I would like to individually select which users I want to ignore. It should be easy to add/remove users from my ignore list.

This would require major architectural changes for the Mattermost server, but adding some use cases to gather feedback from the community.

Server admins wouldn't be able to read the content of conversations because they don't hold the keys to decrypt, which means users wouldn't have to worry about
- Server admins spying on their private conversations
- Governments subpoening server admins into handing over conversations
- Hackers taking control of the server being able to read the conversations

Use local notifications when the app is running or in background. I know that encrypted push notifications are supported when using the enterprise version, but it would be very handy if the app would support local notifications when running in background or foreground for new messages.
This creates the ability to use the app without sending data around the world.

Most popular text editors change the text direction automatically to RTL (Rgiht to Left) when you enter a text in RTL languages such as Persian, Arabic or Hebrew. If that was the case in the Mattermost, we (the RTL language speaking people!) could use Mattermost much more productively, and localization to Farsi, Arabic, etc was possible.

emojis not expressive enough? with sticker packs from telegram, it would definitely spice up your chat in your team!

Add the ability for teams to share "global" channels.

We have multiple teams but have a need for a common channel across all teams.

Original discussion can be found here: https://github.com/mattermost/desktop/issues/111

Add a configurable setting to show count of unread messages, mentions or channels on taskbar.

When a message is received, there is small red badge with number of total unread mentions (in the client taskbar icon and the browser tab).

Proposal is to let the user choose what to count on this badge - any messages, mention and direct messages only or even number of channels with unread messages

Add support for a generic OAuth2 provider for Mattermost Enterprise Edition, in addition to other single-sign-on features for enterprises.