For me, it depends entirely on who I'm talking to, and what the purpose is.
Online, I like the acronyms. I prefer SI over SH, but that's just a matter of opinion. I'm also more likely to use terms like self harm as opposed to mentioning the act.
Talking to my friends who do it, we usually refer to it as "doing something stupid." Or occasionally as cutting, if we're feeling blunt.
When talking to people who don't do it, it gets more complicated.
I usually just tell it like it is. (Cutting, burning, etc...) But it depends on the situation.
The only thing that I really can't stand is when people make hand gestures.
I understand why self-mutilation is commonly used in the professional world, as you are basically damaging a vital organ (Skin). However that doesn't mean I enjoy hearing it.
Question (Kind of.):