John Smith, such an influential figure in the history of art, was a renowned artist.
When the comma before such introduces a restrictive phrase, it provides essential information that narrows down the meaning of the sentence. For example:
The candidate selected such candidates who had relevant skills and experience.
In the first sentence, the comma separates the nonrestrictive phrase "such an influential figure in the history of art" from the rest of the sentence. This phrase adds extra information about John Smith but is not necessary to understand the main point of the sentence.
In the second sentence, the comma before "such" introduces the restrictive phrase "who had relevant skills and experience." This phrase provides crucial information about the candidates that were selected, limiting the meaning of the sentence.
Therefore, whether to use a comma before the word "such" depends on the function and context of the phrase it introduces.