Haha so it has Discord rich integration in it! But it shouldn't do anything if you don't have discord open, much less launch it... I'll have to run it on my end with the itch launcher and see if I can recreate it as well as the UI bug, never seen either of these bugs!
Also there is indeed a pause menu mapped to the start button. I think the input system may have issues with your controller? Which are you using and how is it plugged into your computer? USB or Bluetooth?
Hope you enjoyed despite these issues though!