so i was wondering what exactly is the purpose of changing stance by pressing l2 or lt ?

So you can see the front of your dude. 

There is none. 

I actually don't think it serves any practical purpose.

if you hold it down you can stop yourself from jumping when inputing moves with up.

I think that may have something to do with which foot or arm is front.  Like some characters I think can only punch a certain way with their right hand if it is a front punch.  
I THINK that is why.

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Don't you mean;

" @MooseyMcMan: I donno. Quickly changing stances makes your character look like they are dancing. That's kind of fun! "

" Don't you mean;

"Kwick Kuestion?"

"

at first i thought it was some sort of vestige of the whole change fight style ffrom the ps2 era mortal kombats

" at first i thought it was some sort of vestige of the whole change fight style ffrom the ps2 era mortal kombats "

They said they added it for some purpose, but then decided against that purpose, and they felt it was pointless to take out the stance change so they kept it anyways

They mentioned it during the Machinima live stream somewhere when one of the developers was asked that question, I'm not gonna sit through and watch the whole video to find it though, but I promise its there. lol

EDIT: So my obsessive compulsiveness made me sit through and watch for the time and it starts around the 24 minute mark! :)