Actually the pronouns make important distinctions in the example you provided and are not redundant:
Means, "You want to eat"
Means "You want to eat it", with "it" being that thing that has previously been named and the pronoun "lo" stands for.
Quieres comer? Hay un yogur en la nevera Do you want to eat? There is a yogurt in the fridge
Hay un yogurt en la nevera. Quieres comerlo? There is a yogurt in the fridge. Do you want to eat it?
Me he comprado un coche nuevo. Quieres probarlo? I got a new car. Do you want to test-drive it?
It is the same for "comer-me-lo" or "comer-te-lo"
Hay un yogurt en la nevera. Quieres comértelo There is a yogurt in the fridge. Do you want to eat it?
The "te" is the reflexive pronoun for "you". The reflexive pronoun indicates who is the beneficiary of the action. Reflexives can be tricky to master. You can say "comértelo" to express that you receive the benefit of eating the yogurt, but you wouldn't do so with "probarlo" for the car, but you could do so with "probártelo with something like a suit or jeans
Quieres probarte esos pantalones vaqueros?
Edit to address the latest comment.
You can write/say something like "Quiero comértelo". Imagine that you are playing with your 4 year old nephew. He is in your lap, you are tickling him and then you say "Now I'm going to eat your ears! I want to eat them!"
Voy a comerme tus orejas. Me las quiero comer
There you stress that you are going to eat the ears
Voy a comerte las orejas. Te las quiero comer
There you stress that his ears are going to be eaten, by you. If it is difficult to understand, think of it with the verb "morder".
Me muerdo las uñas / Tengo el hábito de morderme las uñas (You do the action to yourself)
Te muerdo la oreja (You do the action, somebody else receives the "benefit" of the action)
And if you change "la oreja" for a pronoun:
Quiero comérmela / Quiero comértela
So "Quiero comertelo" means that you are going to eat some body part of someone (because they will receive the action). You wouldn't say "quiero comértelo" for someone else's food, since even if the food belongs to them, they are not receiving the action of being eaten.