When loading into a new world or going through portals, your character will spawn in, as expected. It can be hit and damaged. The loading screen will continue after you spawn in though, allowing players, mobs, and other things to push and kill the player. They are unable to do anything though, because the loading screen continues to be displayed. There have been many times where I have fell off the end islands and killed by mobs in nether portals because of this glitch.