Thanks for the feedback! We are working on this.
Current Dark Mode support: https://docs.microsoft.com/en-us/officeupdates/release-notes-office-for-macMarcus commented
It's great that you added the dark mode to the reading pane, I'm using it and enjoying reading mails much more now. The problem is that the UI while writing also should be dark in order to minimize eye-strain. Would be lovely if you could make the writing experience dark as well! Thank you.
17,550 votesMarcus commented
Please add this feature, as well as the possibility of delaying all sent messages to match the features of the Windows client.