When you have one image in a post you click the image once to lightbox it, then you click it again to see it full resolution. But, when you have multiple images in the same post you click one of the images to lightbox, then when you click it again it goes to the next image rather than going to the full resolution zoomed in mode.
I feel the behavior should be the same as a single image so when you click the image in a lightbox it goes to full resolution, and if you want to go to the next image you click the right arrow rather than the image.
I am not sure we even need to keep this “giganti-image” click to see super enormous image that requires scrolling thing. It is confusing. I agree it is inconsistent to get “giganti-image” for single images and “see next” for multi images.
Personally I think we should imply nuke “giganti-image” and have click do nothing I guess unless you have multiple images.
I don’t think that’s necessary, it might be better to have an explicit “full size” link for the image in the footer (alongside “download”, which is a similar option), rather than this secret click to expand, which ceases to work in slideshow mode.
And for the record, @davidkingham, “download” is 95% the same thing as what you want, so you already have a workaround in slideshow mode. Try it.
Another example where zoom is important is extremely tall images. I like the idea of a dedicated “zoom” button, download it fine, but sometimes it’s nice to just stay in the browser and not need another app to open.
+1 for keeping this mode; it’s relevant in our 3D graphics community where people often upload 4k+ images. The extra link sounds like a great solution.
We use this regularly to evaluate the details of larger images when critiquing them, I would hate to lose this feature.
I know this is very similar, but we have public sections of our site that have the download button turned off and private paid areas with it turned on. I know it’s a very specific use case and the reasons are ridiculous but it’s working well for us to give people a false sense of security.
I like the idea of having a zoom button, my only request is that it has its own class in the mfp-bottom-bar so I can hide everything except the zoom button, I don’t want the title/size/download visible. Along the same lines, it would be great if all of them had their own class, right now I am changing the text to be transparent to hide the title and size.
I had already comented on this, in a request for improvements to the lightbox.
I agree, current behaviour is confusing, when you click in the center of an image it should be magnified as when there is just one image, when you click to the right or the left it should change the image showed.
giganti-image demo (make browser small, click then click):
button if we want to zoom
the full size link idea 
