Earlier quoted context omitted.
Sorry, but dropping Markdown support in favor of an input UX that is to this day atrocious gives me little faith in Slack's user stories moving forward. I'm fine if they want to make the default mode more intuitive for a broader audience, but I have yet to hear a good argument for not having a little button to enable raw Markdown mode. EDIT: See comments below for instructions on re-enabling Markdown mode.
Preferences --> Advanced --> Format messages with markup. ̶T̶h̶e̶ ̶o̶n̶l̶y̶ ̶d̶o̶w̶n̶s̶i̶d̶e̶ ̶i̶s̶ ̶t̶h̶a̶t̶ ̶m̶o̶d̶e̶ ̶d̶o̶e̶s̶n̶'̶t̶ ̶s̶u̶p̶p̶o̶r̶t̶ ̶m̶a̶r̶k̶d̶o̶w̶n̶ ̶s̶t̶y̶l̶e̶ ̶U̶R̶L̶s̶ ̶l̶i̶k̶e̶:̶ ̶ ̶[̶e̶x̶a̶m̶p̶l̶e̶ ̶s̶i̶t̶e̶!̶]̶(̶h̶t̶t̶p̶s̶:̶/̶/̶e̶x̶a̶m̶p̶l̶e̶.̶c̶o̶m̶)̶ Never mind, it looks like Slack has fixed this!
Honestly surprised I haven't come across this before.
Also, link formatting seems to be working for me?