Playing since 1.0, LM leech has only ever worked on tai or nin/tai damage. I.E. susanoo itachi's mystery and high to low float chase never gave you hp back.

The only pure nin damage leech that i know of is from either FM or Minato Suit.

I believe there are some ninjas who are mis-labelled Nin attack when they are Tai attacks or Tai/Nin. That may be causing the confusion.

May be late for this, but I just want to add more info regarding leech life abilities for anyone new to this game just like me. Nowadays, there are many powerful ninjas which overshadow the small ninja, such as Kabuto. I don't mean that Sage Kabuto, just Kabuto, the original nerd. If you're building Curse Mark team, adding Kabuto will greatly increase your survivability because Kabuto can heal, remove debuffs and most importantly, any damage cause by Curse Mark ninjas (such as Kimimaro, Sasuke, Anko, etc) will also have leeching effect. BUT, this only applies to Curse Mark ninjas. Thank you and bye.

Oh, wait... there's something about Kabuto does small damage to Curse Mark ninjas. That passive is actually very useful to curse mark because most curse mark ninja get stronger stats when taking damage. That weak damage Kabuto does is actually buff for them, just think it that way. There are also curse mark ninja who lost this ability when you upgrade them, as example Sasuke. Winged-Sasuke gets Ninjutsu and Resistance buff when taking damage, but once you upgrade him to Kirin-ulti, he will lose that ability.

does leech stack? like with LM and guy used together?