It's really demoralizing to be on a team on which the devs clearly have better design and UX sense than the designer(s) and/or product manager. But not the titles—they're "just" software developers who couldn't possibly understand users or design or common friggin' sense.
Sometimes, the devs can sneak in a hidden fix. For example, remember back when VS 2012 made menus ALL CAPS? Officially, that was the brave new world everybody was supposed to live in (https://devblogs.microsoft.com/visualstudio/a-design-with-al...). Users hated it with a passion.
And then it turned out that there's an undocumented registry key to re-enable the old behavior, that was leaked without much fanfare (https://www.richard-banks.org/2012/06/how-to-prevent-visual-...). It was never mentioned in any official documentation, but word of mouth spread it far and wide, and its existence probably spared the worst in terms of angry user rants.
Ironically, the outcry over the caps was big enough that this setting eventually got an official checkbox in a major release sometime later, and then became the default behavior again.
Maybe they have statistics that indicate that their larges user group by now isn't capable of using markdown? Most non-techies are not aware of markdown.
Maybe they have, maybe they don't. Or maybe they can pull some out of their behinds on the spot when asked (which I suspect is the most likely case).
If non-techies can be taught how threading or bunch of other Slack idiosyncrasies work, they can as easily be taught that surrounding text with characters like *, /, ~, _ and ` changes formatting. It's a trivial concept. Reddit, or countless Internet forums before, never had a problem with teaching that to non-techies.
