Re: viewing photos inside the post
I don’t think the attachment plugin is designed to allow those images to be inserted into the post with the allow images plugin. It could probably be done with a 2 step process.
1. attach the image.
2. grab that URL and then insert the image.
It would be in the thread twice though, which is silly. I think it’s better to have the images stored elsewhere then have people insert them like that, nothing on your server.