Hello Brandon,
Big thanks for this code. Using it I've been able to show image descriptions (using for photo credits) only within the Lightbox of a Masonry Gallery Section.
Since then I've tried a few ways to link using different parts of the text to external pages (there may be multiple links per description, 1 for each credit):
First I tried including an anchor tag within the description for the image itself, however it looks like Squarespace strips out the HTML.
Next I executed a Javascript function following the call to "addGalleryItemDescriptions()" in your code.