Slack’s old formatting syntax was Markdown-like but not exactly Markdown, just similar. In case anyone from Slack is paying attention to their technical users here, this is a great opportunity to move to CommonMark formatting for technical users and wysiwyg for non-technical users: just make this optional and switch the format syntax for the non-wysiwyg mode to CommonMark. I can understand that changing the formattin…
Just stick to CommonMark, for god's sake. Atlassian, Slack, take a look at Github's editor experience because it's fantastic compared to yours.