(Low Level?) Low Health Damage Mitigation

Before the crucible, I can’t imagine anyone dying as a level 1 character. These days I do it on purpose around wave 6 to get some quick levels and loot, which seems to be the most efficient way to start a character.

While doing this, I noticed that the damage my character takes is drastically reduced the closer to 0hp he gets. Hits that were doing well into double-digit damage are reduced to 1, and getting closer to 1hp seems to increase mitigation exponentially, eventually leading to the character’s ability to survive a full barrage of multiple hits multiple times with 1 or 2 hp left before finally giving in and crossing over.

It’s easier to notice on a level 1 character with nothing but starter gear because there are basically no other sources of mitigation, resists, regen, etc., and the enemies deal low enough damage for one to be able to watch it happen relatively slowly, but I wonder what is causing this.

Is this just a temporary mechanic for extremely low level characters to make the game slightly more forgiving early on? Does it cut off at a set level or taper off over time? Or is this in effect all the time but less noticeable on higher-level toons because it isn’t a % mitigation but a small flat amount? Inquiring minds must know! I couldn’t find any information about this in forums or the guide.