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
...

We are using HAProxy and multiple subdirectories as internal redirects, to consolidate services.

Right now, Mattermost assumes it is being install at the root of a fully qualified domain name, so moving it anywhere breaks multiple paths for many files.

It would be much more valuable for teams to be able to deploy to "http://www.example.com/chat" instead of always resorting to "http://chat.example.com/".

See: https://mattermost.atlassian.net/browse/PLT-200

Right now there's no approved way to do mattermost on ARM. I think ti'd be a great idea to fix that, and I'm working on fixing it myself. If I get a definitive result, I will post it in the regular forums and/or submit a pull request.

It would be great it mattermost is supported in FreeBSD.
I think in order to support more OS, specially BSD unixes, mattermost should not depend from Docker.
For instance Docker doesn't well supported on FreeBSD.

Like or +1 concept from social networks for single messages.
Should display the number of likes near the message-title.

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.

Mattermost seems to be a good candidate for making a Sandstorm app. Sandstorm https://sandstorm.io/ allows for secure bottling of web-apps. Many of the apps currently in the ecosystem are complementary to Mattermost - in function and ideology.

Currently the list of people under "DIRECT MESSAGES" is ordered alphabetically. In order to find people in this list quicker, it would be useful if the most frequently "used" people would be at the top.

Some users want to view a channel before deciding to join: https://github.com/mattermost/platform/issues/2382

To preserve or moderate a given thread , theme or channel, tagging them makes the search much easier afterwards. But to make sure, that the given hashtags will be the same (tag cloud?), by typing # a dropdown should show up with already used tags. Behavior could be the same lile with @ or :(for smileys!).

Slack provides tighter integration for bots like hubot and calls it Bot Users. Slack's documentation describes it in depth: https://api.slack.com/bot-users

For example, one of the most import advantages is talking to the bot in a private manner (direct message).

It would be great if Mattermost provided this.

When there are multiple threads going on in the same channel, all lines are prefixed by a grey vertical bar. The only way to separate the threads is to read the reference message. If the vertical bars had different colors (randomly selected), it would be easy to at a glance see which messages belongs to which threads.

Currently the web interface has no option to increase the font size. This is plainly silly. Please fix this ASAP.

Now the contacts (Direct messages) are always sorted alphabetically. It would be great to have different options of sorting. What we like the most is sorting by last message recieved/sent, which means on top we always have our most recent conversation (like in Skype)
Any chance to have it in future?

Add an option to allow changing of the default "Display" settings from the System Console. (E.g set Theme & Teammate Name default "Display" settings globally).

I'd like a way to post information for the team that only I (the admin) can edit. In order to do this, I'd like to lock the channel so everyone can read it, but not edit it except selected users or only the sysadmin.

Direct Message yourself for private notes, etc, like Slack: https://get.slack.help/hc/en-us/articles/219899267-Saving-private-notes-and-files