I was indeed one of the persons that got hit by a lot of achievements all of a sudden while taking a quick peek on one of the multiplayer servers out there Any way to 'delete' this achievements so I can get them myself?

Using a Mac I switched fullscreen using the OSX menu bar on the top, and also used the full screen toggle in the graphics settings. Those are apparently not the same setting, after some back and forth to get back to windowed mode Factorio crashed. See attachment for log. Not a big deal, but it asked ...