Are you referring to this paragraph?
This says that a power that deals damage type X is an X effect and hence has the X keyword. It also indicates that a power that has keyword Z might deal damage of Z type or have some other effect that is Z-ish in character. But it does not say that every effect of a power with keyword K is a K effect. Nor does it come anywhere near implying that. In fact, at least as I read it, it strongly implies that each keyword of a power is associated with one or more discrete components of a power - for example, that a power with the acid and poison keywords that does acid damage and inflicts the slowed condition has two effects, one an acid effect (the damage) and the other a poison effect (the slowed condition).
Let's look at this thing:
'A power that deals acid damage is an acid effect and thus has the acid keyword.'
Using that phrase, we then examine this power:
Caustic Rebuttal DracoSuave Feature Power
Encounter - Acid, Implement, Psionic, Psychic, Fear
Attack: Charisma vs Will
Hit: 2d6 + Charisma modifier acid damage, and the target is pushed 3 spaces. The target is slowed (save ends)
Aftereffect: 2d6 + Charisma modifier psychic damage.
Alright. That's a cluster%%%% of different effects, and so it makes a good example.
Now, does this power deal acid damage? Yes. Therefore, VERBATIM ACCORDING TO THE RULES, the POWER is an acid effect.
Is the aftereffect part of that power? Yes. Is the aftereffect part of an acid effect? Yes. Therefore, the aftereffect IS an acid effect.
A power that has the poison keyword might deal poison damage, or it might slow the target, immobilize the target, or stun the target. But the poison keyword indicates that it’s a poison effect, and other rules in the game relate to that fact in different ways.
This here says that a power could have the poison keyword, and that keyword could be dealing with all sorts of different things. BUT, it's a poison effect. The POWER is a POISON effect.
That means that effects of that power are themselves poison effects.
I don't see how 'But the poison keyword indicates it's a poison effect' means 'it is not a poison effect except for the parts that are likely poison' as opposed to 'the keyword means its a poison effect.'
As for the caveat that immunity == infinite resistance, that is no where mentioned nor implied in the rules.
Let's make this clear: Customer Service is often wrong, and has given two different interpretations in this thread. They've come out with rules interpretations before that are diametricly opposite to that mentioned in the rules. They've made claims that spirit companions are creatures, that weapon focus does not work on staffs, and that fighter's marks can stack with each other.
In fact, here's a misconception you need to clear up swiftly.
Customer Service is NOT WIZARDS OF THE COAST.
wizards.custhelp.com is a subset of custhelp.com, which is how the company
RightNow deals with customers on behalf of their clients.
It isn't a room in the WoTC office where gamers gather to playtest the latest D&D stuff and play magic between responding to emails. It's a place where a -third party agency- hires people to take care of this, who may or may not be experts, or may just be people making 8 bucks an hour and have no knowledge of D&D short of what training they get in the door.
They are NOT a primary rules source, and it's irrational to think they are, or depend on them. My guess is that they are Rightnow employees who play D&D and are about as well versed in the rules as anyone here. That makes them as much an authority as anyone posting in this thread. No more than that.