The HTML5 spec doesn't have .addItem() for the history interface as far as I can tell, so I can only presume that's up to browser implementation what it does if anything. The spec states you use .pushState() to give it something new (or .replaceState() if you don't want back button to get to the previous one) and that the .state property has the currently seen one as modified by the browser itself. I'm only hobby web developer myself, so don't take my word as claim of absolute truth.

For reference: https://www.w3.org/TR/html5/browsers.html#the-history-interface

This should be easy to implement considering it's the inverse of SFW mode, but unlike NSFW mode, it doesn't show the SFW part too.

Useful also for people who like making multiple variants of the same drawing (e.g. differently clothed versions of same pinup), or just want to bundle up multiple stages of the same one (e.g. sketch, ink, and colored versions all in same submission).

I would upvote this only if this was an option for the submission uploader to enable if they wanted it and would be off by default for new users, because I know there are actually artists who like this kind... feedback.

I hope it gets optimized, as currently it's a massive memory hog after scrolling a little while like most endless scrolling is.

https://dannysu.com/2012/07/07/infinite-scroll-memory-optimization/ has some investigation on how to deal with that memory problem in general, not sure how comprehensive it is, but it looked very promising.