Spicy food, like Chili peppers, to avoid being eaten, evolved a flavor animals can't tolerate. That flavor comes from a chemical called capsaicin, which burns our mouths. Even so, we eat them - that's because our brain knows survival can depend on pushing the limits. A red chili contains four times the vitamin C that's in an orange. So that we can absorb that essential chemical, our brain has learned to overcome discomfort. During this process, the brain releases endorphins, natural painkillers that induce sensations of pleasure. The chili's heat activates the brain's learning center and stores the memory, that despite a fierce flavor, chilies are rich in nutrients and a peculiar pleasure.

Your brain has the ability to use a similar tactic in other situations. Whenever your body knows it needs a certain nutrient, it triggers the "want" feeling for a certain food it knows to contain this nutrient and triggers the sensation of pleasure after you eat it.

"Everything's fine in moderation" is valid here, but you don't need to think about it, really. Your body knows when it has enough. If you eat a certain amount of chili, your brain knows you don't need it anymore (for a certain period of time) and it won't release the required endorphins for you to eat and enjoy more of them.

"Being addicted to" in this sense means if you were addicted to endorphins in such a way that you would actually inject them intravenously. That of course is very wrong (unless it has got a medical reason, which in this case is completely irrelevant). If the endorphins are triggered by your brain and released by your own body, it's ok, because it knows how/when to stop.

The same can be applied to adrenaline. You can inject yourself with adrenaline shots and you'll be a junkie. Or you can do extreme sports and let your brain release your own adrenaline. This way, you won't be a junkie :)

Of course there is a possible harm, like there's a possible harm with every other food additive. Salt, for example. You mentioned liver. As liver plays a major role in synthesis and metabolism, all the food additives are processed/filtered here. If you have liver problems, it fails to process them. Abuse the salt amount in your diet, you give a hard time to your liver. Abuse the Chili amount in your diet, you also give a hard time to your liver. It's just a general rule you should follow with everything you eat.

If you love spicy food, eat it, there's absolutely nothing wrong about it, but be reasonable about it just as you are reasonable with everything else - salt, sugar, etc. When your body doesn't want it, it will tell you by not liking it and if you listen, you'll be just fine.

It really depends on what it is that makes the food spicy. Capsaicin acts as a good anti-inflammatory ^[1], but it is often found in spicy dishes that contain fermented items, which can trigger headaches ^[2] due to their high levels of tryamine. As for your liver, I think the concern may be with triggering excess bile production, especially if you have gallbladder issues or no gallbladder at all.

If you can tolerate spicy foods without the common symptoms of intolerance, I see no reason to stop enjoying them.