Earlier quoted context omitted.
Does slack even use markdown? It seems to me that it just uses some markdown-like sybtax as a shortcut for generating its rich text. Like Google Docs will start a list after - .
Ehhh there's "Markdown" and there's "markdown". Slack definitely has markdown, and any argument to the contrary is a "No True Scotsman" fallacy. I personally use hyperlink text, bullet lists, tt/bold/italics, quote blocks, pre blocks.
In ~2019, it changed to "WYSIWYG with markdown converted to WYSIWYG as you type". If you type "Hello *world*" the * will disappear and the "world" will be bolded - and you can also get bold with Ctrl+B or pressing a 'bold' button or pasting bold rich text.
There's an option to disable it [1], so if your slack experience is different you might have WYSIWYG disabled.
And if you think markdown usually means *foo* producing italics, and **foo** for bold, all I can say is yes.
[1] https://twitter.com/slackhq/status/1201955273667158023?lang=...