[aznpwnzor]

Unfortunately the review doesn't address this but there are multiple factors that can explain this while keeping the mutation rate of language the same.

It may be hard to separate the 3 factors that come to mind:

1. higher volume of communication. (more people than ever write/read more than ever)

2. lower bar for observable/written down communication. (anybody can write publicly/permanently)

3. faster transmission of previously local slang. (more groups that previously would have kept their slang to themselves are interacting than ever, e.g. your non black friends ruining the word "ratchet" before 2014 ended)

and by slang here, I mean both verbal and grammatical

[dredmorbius]

Earlier histories of communication changes, particularly JoAnne Yates, but also James Beniger and Elizabeth Eisenstein, note (along with societal impacts) the stylistic shifts in writing precipitated by technological changes.

Telegraphy promoted telegraphic style, typography promoted cliche and stereotype, the press itself both vernacular and literacy, along with notions of authorship as opposed to (classical) authority.

[Alex3917]

All the factors you mention are true of course, but I'm not sure any of them really explain it. In my mind the Internet is something like a skate park for language, where you have this global infrastructure for developing, rewarding, and disseminating new tricks.

Just increasing the volume of people writing books and letters doesn't get you K5 or 4chan.

[EGreg]

New tricks? I feel like in the past, everyone had language tricks. Speaking in fun ways, clever one liners and turns of phrase of the type Mark Twain or Churchill would employ were commonplace. People didn’t have videogames, facebook and other stuff to amuse themselves, or express themselves through. They found ways to do it through language.

Just pick up any book that captures how people spoke in the 19th and first part of the 20th century. Language was sport.

[pretendscholar]

The written word is only part of it.for example, the self imposed constraints of the twitter can increase the need to pack more into one message coupled with the ability to add an image creates weird selective pressures on language.