Teams and Slack as well, though they use an odd variant markdown (where single asterisk indicates bold instead of italics).
What things like Slack and WhatsApp use are not variants of Markdown, but entirely unrelated lightweight markup languages <https://en.m.wikipedia.org/wiki/Lightweight_markup_language>.
As for Teams, it looks like it’s much closer to Markdown (uses the same idiosyncratic/stupid link syntax), but still significantly incompatible even if they call it that. And my guess (as a non-user) is that it’s just an input method immediately converted to HTML or similar, not retained as text. So in that way it’s not Markdown either.
My least favorite Teams markdown idiosyncrasy is using (foobar) for emoji search instead of :foobar:
Technically speaking, Slack's markup language is mrkdwn.
That’s not technically, that’s marketingly (sure, it was presumably developers that named it, but it’s still marketing). mrkdwn is a horribly misleading name and they should feel guilty. https://hn.algolia.com/?query=chrismorgan+mrkdwn&type=commen...
I get bold and italic confused because Google Chat is almost-Markdown except for * being bold and _ being italic (whereas it's double vs singular in classic Markdown).
Teams does not use Markdown AFAIK. I wish it did.
See https://support.microsoft.com/en-us/office/use-markdown-form...
My company is on Teams and I regularly use Markdown in my messages, though I still struggle to remember that I have to use underscores not asterisks for italics.