Any news on this? Autocompletion of nicknames with initials + tab is a standard since IRC, and should be available in Mattermost too. @nicknames are a different thing, and allow linking user nicknames, but simple and more straightforward highlights are still very useful.

Is there any way to customise the behaviour of Mattermost until a new versions fixes this officially?

I agree with Patrick, this should work without the @ sign.

It only works with @, would it be possible to autocomplete with tab like on most irc clients and Slack/rocket.chat.

For instance if I want to autocomplete Timmy I could type T<tab> instead of @T<tab>

This is more a bug that a feature, and we should fix it...