In order to use the gallery field on the front end of the site the logged in user must have permission to manage media files. For the rest of it you’d need to look at how the comments are shown and customize that output to show the images. I don’t know what would be involved in spitting comments into two areas, like I said, this all has to do with the way the WP shows comments and you’d need to look into that in the WP docs.
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