goodness, i might be too late to this thread! it's been more than a week! you might've finished your essay already!
but just in case, i wanted to point out that homestuck was not just a work of fiction, it was also a community-building exercise, and that's what really gives it its position in internet history. hussie had at least a cursory understanding of the various tribes/archetypes of the ancient internet that existed in the early 2000's, and many character designs (the trolls in particular) were based on them. this took place during an era where social media was still new, having "internet friends" still made you an outcast, and internet culture wasn't taken very seriously. like people shared our memes and so on but we were generally regarded as losers by mainstream IRL culture.
so you have this assertive celebration of ancient internet culture, plus a staggering amount of content based directly on community input, discussion, and memes. a lot of the jokes are removed from their original context for the archival reader - if you want a good example of this, look up the Pantskat meme. along with this, hussie frequently reached out to community members to make various contributions - calliope's art was produced by a popular fanartist, as one example among many. there was a tremendous effort to make the readers feel like a part of the story!
if i wanted to summarize what homestuck is in just a few words, it would be "internet Woodstock" - a massive gathering of a specific subculture around an online stage.