i've always had this question..
when u have a follower with u it is very well likely that during hard combats u are going to accidentally hit ur follower because he or she always gets in the way..
that is my problem as of now, i am playing with jordis as my follower/wife to take on everything we can find, she's well built to take on alot of damage, she can take on forsworn briarhearts already with some decent damage recoil from every hit she takes but i dont know if she is levelling up with me or not however i find her AI pretty much screwed since she's a warrior.
i cant blame her for jumping straight to action but when i accidentally hit her, my heart starts to bleed seriously.. she says "STOP i'm in your side!"
and im like "omg omg omg im soo sorry..i didnt mean it..but u got in my way" after that i use the restoration spell heal other and she says thanks and i feel way much better psychologically too...
so since the tittle is kinda weird here's my question..
if u hit ur follower once in a while like i do accidentally, will they eventually turn on u and start attacking u back?
because i've seen videos of people trying to kill lydia and she only takes on a few hits and then she loses her patience and attacks back at you.
So much for "protecting me with her life"
i understand their role as housecarl is very important but lets face it, they ultimately care about themselvs first. that applies to every follower u have..some more than others? i dont know..give me ur opinion on this matter because i'm kinda lost here..

Yes, eventually, they will attack back. I think all npc's either fight back or run.

yea but like when i hit her it's only once at a time not like im hitting her 3 or 4 times in a row. sometimes i accidentally hit her with my sword, sometimes it's with my spells or fire breath..it depends..

If a companion gets low HP they turn on you but by then one more hit and they usually die.

I think its a three strike rule, and the strike resets when she recovers full health, not after a few seconds. I am talking out of my ass though, so don't take me at my word. I'm usually just try to be careful

same here im super carefull
if she ever gets angry at me ( even though i treat her well) i will have to reload the game again
i've lost count of how many times in seperate ocassions i have hit her accidentally but then again so far soo good..she has a TON of health so maybe she didnt turned on me because every attack i accidentally lay on her does like only a small scratch..she's super bulky..

A little trick.
If you are playing a ranged type have a shield types NPC. They go in close and you avoid hitting them.

If you go melee, have them as bow only. or magic but most followers are best with a bow I think. Solved my problem with hitting them all the time.

I just encountered this problem for the first time last night. I'm playing around with my first summoned Atronach, and it seems that whenever my mage has a fireball perfectly aimed at an enemy her Atronach picks that exact moment to get in the way. When we're traveling across country and my mage gets ambushed by a Saber Cat the Atronach is like half a mile away. But let my mage line up a tricky shot and all of a sudden the Atronach ctly has to be directly in the line of fire. *sigh*