Slack brings back message formatting with Markup under a non default config
"Hey there,
We're writing with an update on the message composer. We're pleased to share that we have added a preference that will allow you to format with markup. You can turn this on from Preferences > Advanced > Format messages with markup. Once this is turned on, you will no longer see the formatting toolbar, and the experience should be similar to what it was before the change was made. Please note that this change applies only to the desktop apps and supported browsers.
If you're not seeing this option, please reload with Ctrl + R (Windows and Linux) and Cmd + R (Mac). It may be necessary to reload more than once in order for this change to take effect.
There are some limitations to keep in mind if you choose to format messages with markup, and you can read more about those in our Help Center: https://slack.com/help/articles/360039953113
Once again, we'd like to apologize for the disruption this caused to your existing workflows. We appreciate the time you took to write in with feedback, and are grateful for this opportunity to improve.
Please let us know if you have any thoughts on the new preference, or if there's anything further we can do to help."