Mediawiki (the thing behind Wikipedia) actually lets you transclude whole pages and it's also the way its templates work. It's pretty cool because you can also

Mediawiki (the thing behind Wikipedia) actually lets you transclude whole pages and it's also the way its templates work. It's pretty cool because you can also have options to not include certain info inside <noinclude> tags and some templates such as for episode lists even show less information when transcluding. Oh and you can also transclude specific sections IIRC. By linked into, are you saying by URL? I notice that archive.is actually adds its own links to the side like a ruler. I think the status quo of linking only to headers is okay, but maybe you're envisioning something like linking to specific words in sentences. That would be great for quoting but the HTML would probably look/load horribly. Maybe there could be a system that let you link to offsets so it wouldn't need actual anchors in the source, but those could break with a simple addition of a word at the beginning. It's an interesting problem for sure.