> The argument here is scoped to people who have some degree of mastery over the language but are being sloppy with their written communication, which is to say "careless and unsystematic; excessively casual".

I think there are some good points here for technical writing. But it's easy to forget how memorable playful communication can be.

E.g. a responding via haiku or something no-caps and full of enjambment, might be extremely memorable. (especially in a chat full of technical writing style).