I'm sure in the past when I have linked to my images on Flickr that the forum software has been able to pick up the EXIF data from Flickr, even when I have made the images private.
I used a Publish service from LR in the past, that made the images private as part of the upload process. I then had issues with Flickr, and didn't post anything via them for a while, and when I went back to them the Publish service would not link correctly. So I was doing manual uploads, and setting the images to private, and I am sure that for those images AMASS could get the EXIF data OK.
I have now upgraded to LR CC and discovered that I could get LR to link to Flickr OK again, so I have used that the last couple of days, but it seems that the forum now can't see the EXIF. I'm linking to the original image in the size option for the Flickr BB Code, which should have the EXIF included, it is visible on the Flickr site when I view there.
I would sometimes rather not show images on my public Flickr feed, but still want somewhere to host images so I can potentially post more than two images within a post.