They have. It’s called Webpack. There are also various similar tools.

EDIT: I got downvoted for telling the truth? The website is here if you don't believe me: https://webpack.js.org/ It literally does what the post I replied to asked for.

I've noticed an increase in upvote/downvotes based on whether or not a person agrees, rather than whether the comment was on-topic and contributed to the conversation.

I try to make a point of upvoting comments I disagree with, but that are clearly made in good faith in order to counteract this trend.

I suppose this problem is a normal low entropy state in community moderated systems.

It takes a lot more mental energy to moderate based on the value of the conversation rather than whether you personally agree.

The older HTML equivalent would be to package it in a *.mhtml where the various parts are mime-encoded, like a multipart email would. It's only been around for decades. Creating it was saving a webpage in IE. Mozilla/Firefox never supported it, though, even though they already had the necessary code for doing email… possibly because they had inherited the Netscape mail codebase which was a bit difficult to reuse.