Right now the scope of the search feature is limited to the current team. It would be great to have option allowing to specify the scope: channel, team, global (for example)

The Android app requires the Google Play Services because it uses GCM for push notifications. This library is not open-source so it prevents Mattermost from being included in FOSS repositories like F-Droid.
It would be nice to have an option that builds the app without GCM.

The second generation mobile apps currently are not designed to support tablets.

(See https://github.com/mattermost/mattermost-mobile/issues/670)

If you would like to see tablet / iPad support, please help upvote this feature idea so we can track the demand for it.

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).

It would be great to make admins life easier to develop an auto admin function to Mattermost that on click downloads, installs and updates the given installation, so the admin doesn't need terminal or root access anymore. Especially renewing the config (put the existing entries in the new/extended config) would be helpful.

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.

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!).

Just to expand on the original idea located here:

https://mattermost.uservoice.com/forums/306457-general/suggestions/17128663-configurable-away-time

Auto-away should at least be configurable in terms of minutes, or an option should exist to disable it completely. These settings should exist per user, but I'm not sure how much value it would add if the administrator determines the configuration for the team.

Add support for multiple lines in tables.
From: https://github.com/mattermost/platform/issues/1557

Currently it is not possible to have notifications triggered based on keywords, for example if there are any emergency keywords, a certain ringtone or vibration (or both) will be triggered.

This would be important in the event of any emergency that requires immediate action.

I think it would be a great idea to add spoiler tags like message or message but for spoilers (i.e ^This is a spoil^)

There are several ways to implement this:

-By having an expand/close button for showing/hiding the message
-By having to select the text to see it
-By having to hover on the text with the cursor to see it (might be problematic for touch-based devices)

I suggest discussing on what is the best for mattermost.

Add to jira plugin features to notify about new comments, description changes, attachments changes in a ticket.

Mattermost has a manual Do Not Disturb feature, which is nice. However, it would be extra nice to have "Do Not Disturb hours" for each account, so individuals can set certain hours when Do Not Disturb is automatically enabled for their account. It would be extra nice if these were automatically set on account creation to common bedtime hours in the local time zone; for instance 10pm to 7am. This is a nice work/life balance feature that encourages people to get enough sleep by default. :-)

Matrix.org is an open standard for decentralised communication, providing simple HTTP APIs for text chat and VoIP calling and conferencing. It would be great to be able to talk Mattermost <-> Matrix!

Would be fantastic for my team to be able to have a static voice channel to join instead of creating a conference every time.

It was nice in Slack to say for the batch of invitees that have been recently invited that they be thrown into channels x, y, z instead of having to manually Add Member to varying channels or ask them to seek out channels and add themselves.

Our team documents project features by posting and re-editing posts. (They can then be flagged, or in future, made sticky, to keep them at hand.)

What would be useful here is to make a post that I choose to allow others to edit, in a wiki or confluence-style.

Support Gitea's OAuth2 provider as an authentication source.

Currently, the team edition only supports GitLab as an OAuth2 source. GitLab is pretty heavyweight and many people prefer other software for a variety of reasons.

Gitea (https://gitea.io/en-us/) is a really nice open source, community supported Git server. They recently added support for acting as an OAuth2 provider (see https://docs.gitea.io/en-us/oauth2-provider/ for documentation). It would be great if Mattermost would support Gitea as an OAuth2 provider.