> You're telling me that "it" or "they" riddled more often than otherwise does not negatively affect search results?
Basically. More specifically, I would say that using definite pronouns improves search results.
> Pronouns increase the chance irrelevant results.
No, because there is no reason to search for definite pronouns, you search for the nouns that are the antecedents of definite pronouns (since using a definite pronoun requires using a noun as an antecedent in writing -- this can be substituted by gesture or other non-verbal cues in oral communication.) And if you use pronouns, you get less result clutter for those searches for the same reasons that you get better readability, you have less close-proximity repetition of the key nouns.