[This reference](https://www.reddit.com/r/learnspanish/wiki/index/faq/#wiki_.2022_omission_of_complements) describes some nuances of meaning when complements are omitted.
It seems to also imply some rules about when complements can be omitted, but I’m not totally clear on that. **So I’m looking for any general advice you can give me about when complements can be omitted.**
The above reference gives the following example:
>Le dieron el premio. / **A ella** le dieron el premio.
Based on the above reference, analogies to similar cases covered in the RAE, and on some interactions online, I have **guessed** the following rules. **Are these approximately correct?**
1. Almost always, in a sentence like the above when the complement has the structure “a [phrase describing a person or living thing]” and a corresponding pronoun is also present (“le” in this case, the complement may be omitted. This is grammatically correct but, depending on the situation, may be confusing or odd-sounding.
2. Often, in a sentence like the above, but when the complement has the structure “a [phrase **NOT** describing a person or living thing],” even if a corresponding pronoun is also present, it is not a good idea to omit the complement. At best this is confusing and people will assume that the corresponding pronoun refers to a person; at worst, this is ungrammatical. For example, I have been told that “Le envié una carta” **cannot** be used to mean “I sent a letter to it” if “it” refers to the city of Paris.
3. However, there are exceptions to #2. For example, I think that [this answer on StackExchange](https://spanish.stackexchange.com/questions/41414/a-los-problemas-del-mundo-no-les-doy-mucha-importancia-no-les-doy-mucha-i/41422#41422) is saying that the following sentence is allowed: “No les doy mucha importancia.”, where “les” refers to “A los problemas del mundo.”
**(There are all kinds of reasons why my inferences could be wrong.** In particular, #2 presupposes that I am correctly identifying what counts as a complement. For example, I think that “a París” represents an indirect complement in the sentence “Envié una carta a París.”, because “París” seems like the recipient of the letter. But I could be wrong; maybe the phrase “a París” is serving some other similar grammatical function.)