When something has "significance" or "meaning" or "value" it is usually relative to the person. What is the person who finds significance in something called? Is there a word for it?
2 Answers
appreciator (n.)
A person who appreciates something; spec. a person who recognizes and esteems worth or excellence in something
appreciate (v.) To recognize as valuable or excellent; to find worth or excellence in; to esteem. OED
Someone who appreciates a given thing, especially:
Someone who values something highly. Wiktionary
In order to feel greater resemblance to the art work, the appreciator simultaneously engages in additional creative activity through "subjective action." Subjective action means that the appreciator adds his or her own subjective elements to the object (art work), thus adding new and additional value to the value already created by the artist. The appreciator then enjoys the enhanced value as the value of the object. Sang Hun Lee; New Essential of Unification Thought
SECOND-ORDER VALUES
Let's explore the diversity a little, the values for which one might enjoyably admire something.
An appreciator's enjoyable admiration, usually if not always, involves not only recognizing a thing's value—recognizing the marvelous job it does of opening our eyes to important truths, for instance, of how wonderfully suited it is for providing safe and efficient transportation; one's admiration also involves recognizing the creator's accomplishment, the talent and skill a person demonstrated by producing something with the value. Kendall Walton; Marvelous Images: On Values and the Arts
As ideal appreciators we would, by hypothesis, all value the same works of art, and to the same extent. Steven Cahn et al.; Aesthetics
As a result, difficult art presents a motivational problem for the novice appreciator. The novice appreciator can't recognize the aesthetic value presented by the artwork until they've engaged with it for a while, but they have no reason to decide to engage with it, because they can't yet perceive its value. Mary Beth Willard; Why it's OK to Enjoy the Work of Immoral Artists
The famous Scottish preacher Alexander Whyte was known as an appreciator. He loved to write postcards to people, thanking them for some kindness or blessing they had brought to his life. W. Wiersbe; Pause for Power
The term for "the person who finds significance in something" is different depending on the theory. In traditional communication theory, such as Shannon, it's enough to say that it's the receiver. In game theory, there are sender-receiver games. In messaging, it's the decoder|receiver. In traditional semiotics, I think that would just be the "recipient of the signifier."
But because of your emphasis on a person and on finding significance, I think you might want to look at Pierce's emphasis on the interpreter for successful signification (for intro, see https://plato.stanford.edu/entries/peirce-semiotics/).