I was looking over the LoSH complete rules book and saw on page 22 that a power that deals 0 (zero) damage can be modified. Does that apply to incapacitate? And if so, what else does it apply to?

Because of the bolded line, most ways of increasing damage (Enhancement, Perplex, etc) won't work on Incapacitate as they all affect damage value. Critical hits, however, affect damage dealt, so critical hits will increase the damage on an Incapacitate attack.

It is true. There is a difference between an attack that deals 0 damage (Incapacitate) and one that deals no damage (Mind Control).

In certain cases, though, like Incap, other restrictions prevent some modifications. With Incap, the power states that the damage value cannot be modified. This prevents Enhancement from working with it. However, the damage dealt can be modified with critical hits and other such things.

I dunno if i'm the only one that realized this or not, but when you roll a crit miss on mind control then you dont take damage.

Likewise, you don't deal one damage when you roll a critical hit on a Mind Control attack.

It is actually any "no damage" attack. Other ones include Taunt and TK (to toss your opponent's figure).