Brian Cronin wrote an excellent article regarding X-Men 100, 109 and 110 – that covers Claremont’s usage of Kitty Pryde, having her leave the book, having the plot disappear, and her return.
I sort wish this was written, when I was originally writing my reveal for X-Men 100. As I had to scan all of my own pages for that review.
https://shadowandflamewithmagik.com/2015/11/13/x-men-100/
At least, others will have the great resource.
I didn’t know, from the comments, that I needed to buy Gambit Volume Three Issue 20, so that’s on my Wishlist now.