The other answers have provided nouns referring to "a love of language" and verbs denoting "pampering," so I'd like to provide some adjectives that I believe convey the "extreme care and attention" (and thus, one might say, the "devotion") to which you refer in your question:
fastidious: very attentive to and concerned about accuracy and detail.
"He chooses his words with fastidious care."
scrupulous: (of a person or process) diligent, thorough, and extremely attentive to details.
"The research has been carried out with scrupulous attention to detail."
NB: Colin Fine, a fine and fastidious user himself, suggested the former in a comment. Props.
Granted, these two words are not used exclusively to refer to care and attention to language, but (as the example for fastidious shows) they can certainly be used in this context.
Of course, there are adjectives that describe those whose fastidiousness and scrupulousness with language (combined with an artistry that results from devotion) produces good speech and writing:
articulate: expressing oneself in clear and effective language.
eloquent: fluent or persusasive in speaking or writing; clearly expressing or indicating something.