Long time geek, fangirl, mother, and reader. I've got a lot to say, you might not like it all, but it will be honest and hopefully helpful.
"Rather than seeing writing as an isolated activity, she saw it as a part of a collection of related and reciprocal tasks."
This kind of critical analysis is nothing new in fan communities, but the internet gave fans a public platform to more widely share their insights. Why this isn't explained in a section of the book about how the internet changed fandom is bewildering.
"Very active fandoms were still small groups—by today’s standards—but they were laying the social, procedural, and cultural groundwork that has influenced every fanwriting fandom since."
The use of "fanwriting fandoms" is incorrect and misleading. These are fandoms first and foremost. They are communities in which all forms of fan works are created. They are NOT fanwriting fandoms.
The only time I've seen fanwriting fandoms (or communities/groups) was in the Twilight fan fiction fandom, which had several small sub-communities of fan writers who focused on their own work.
For example: The Fictionista Workshop, which has since been rebranded as The Writers Collective, began as a community of Twilight Fan Fiction writers conducting workshops to assist each other in writing their fan fiction. The also sponsored fan fiction writing prompt challenges called WitFit. This community, and others like it are fanwriting communities, where the focus is writing and not the source material the writing is based on.
One could even go so far as to call Twilighted and The Writer's Coffee Shop fanwriting fandoms or communities. Both sites elevated the work of writers above the fandom of their origins and even launch publishing houses. The Omnific (Twilighted) and The Writer's Coffee Shop went on to sell fan fiction as "original" novels, one of which is the most (in)famous published fan fiction, Fifty Shades of Grey being one of them.