The single-parameter {{GENDER:|}} does nothing, it just indicates to translators that they may use GENDER in their translations (and displays its single parameter), so embedding the second “you” in {{GENDER:|}} wouldn’t make any difference.

In T332164#8723121, @matmarex wrote:

I wasn't sure where the markup should be placed in English. I had a look at existing uses: https://codesearch.wmcloud.org/search/?q=%5C%7B%5C%7BGENDER%3A%5C%7C&files=en.json. In most cases the markup is placed on the pronoun "you" (if it's used in the sentence) or on the verb, and only once per message, so I followed this convention. (Even though in translations, it can affect other parts of speech and entire phrases, but I think this is intended to make it less distracting for translators working in languages without gender distinctions.)