Tight is a Chrome extension I built that increases readability, removes many redundant/useless buttons, improves the page layout and modernizes the overall style of Slack.
It might be nice if someone started a collection of all the open source Slack improvements that were shut down or died off so that other developers can pick and choose what they like and continue evolving Slack in a somewhat distributed way.
It is open source (https://github.com/RileyTomasek/tight) to encourage community contribution. Suggestions and pull requests are highly encouraged!
Tight was heavily inspired by and owes great thanks to Refined GitHub [1] and Refined Twitter [2].
[1] https://github.com/sindresorhus/refined-github
[2] https://github.com/sindresorhus/refined-twitter