Just out of curiosity why can we stab ourselves in ieytd 2 but not in any of the others

I imagine it's based on the individual rules from each game. As for the specifics of why those are the rules for each game, I wouldn't know, as most were in place before I was active in the community.

yep. I just grabbed the rules off of each existing default "die%"

that's due to there being 2 die% categories in IEYTD2 (where the category was invented). when the category got ported to the original, they elected to just have a no shoot/stab rule (technical note, it's very hard to stab in IEYTD1 due to handling of weapons)