I have already read some material about the difference between the verbs "comer" and "comerse":
- ¿Cuál es la diferencia entre comer y comerse?
- El uso de "comerse"
If I understood right, "comer" is neutral and "comerse" is used to express emphasis on the completeness of the action of eating (as "eat up"). In some contexts, it may also imply voracity or delight in the action of eating.
The confusing thing is that some people state that "comerse" is only used and it is the only correct verb when there is a determinate amount of the thing eaten (eg la manzana, esta manzana, una manzana, dos manzanas, etc). Is it indeed the only correct option or is it just usual to use it whenever there is a determinate amount ? If it is the latter, is it indeed usual in all countries which speak Spanish or is it a regional thing? Notice that "eat" and "eat up" have no such restrictions in English.
Examples for discussion:
- Como chocolate todos los días (OK)
- Me como chocolate todos los días (wrong)
- Comí una manzana. (OK or wrong?)
- Me comí una manzana (OK, emphasis on completeness)
It would be helpful if people answering this question mentioned their country in the answer.