I saw my picture on your blog, but I don't like it. I feel uncomfortable about it.

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In these sentences, what does 'it' refer to?

1. my picture
2. your uploading my picture to your blog
3. or else....

In that sentence 'it' refers to 2, the uploading of the picture to the blog

I disagree with Moon.

Although #2 may be the overall intent, the actual antecedent for "it" is "picture."

In the given context, the word 'it' most likely refers to the action of "uploading your picture to the blog." However, without further context, it is difficult to determine the precise referent of 'it'.