If I'm prone, it's impossible to crawl through doorways, either going into the building or exiting it. It just glitches as if there's an invisible wall in the way.
In real life it would be no problem and in some situations it can be useful to check outside without having to stand up, or to get a better position for engaging the enemy.
Go prone.
Try to crawl into or out of a building.
All of the above is mostly true to the best of my knowledge. Granted not dying by just running through the doorway is a welcome enhancement. :P
One the 'wth' moments I'm sure everyone goes through. I have managed to get through a few though. So not sure if it's an animation thing or perhaps some building weren't constructed properly. Can not say it happens all the time, but would say, most of the time you can not.