With the coming of the new VC book, it seems a popular topic of debate is whether IoN can affect characters. The rules, are a little murky, so here's what we have to work with.
Originally Posted by VC Army Book, pg.26 "Resurrecting Fallen Warriors"
Some magic spells and items can resurrect fallen warriors in an Undead uint by restoring a number of Wounds' worth of models to the unit. If the target consists of a single model, such as a lone character or a Corpse cart, then it can never exceed its starting Wounds value.
And then later in the rule:
[quote=VC Army Book, pg.26 "Resurrecting Fallen Warriors"]A unit cannot usually be taken beyond its starting size, though certain powers, spells and special rules may provide exceptions. Unless specifically stated otherwise, spells and magic items that restore lost Wounds cannot heal characters or their mounts. If a character has joined a unit, only the unit will recover lost Wounds.]
And, just for completeness, here's the BRB rule for Lone Characters:
Originally Posted by BRB, pg.96 "Lone Characters"
Characters that have not joined another unit are treated as a separate unit of the appropriate type for all rules purposes.
So here's my synopsis of the problem. The first quote mentions lone characters, clearly indicating that they are viable targets of IoN. The second quote is dealing with the extent to which IoN can affect a unit. It is basically saying that 1) The unit cannot exceed its starting size, unless stated otherwise, and 2) If the unit has a character joined to it, the character cannot benefit from IoN.
So, as I understand the rule, lone characters can benefit from IoN, but if they join a unit, they will not.