crashtxt, the twitter account, appears to be mostly the net art legend, jimpunk, but I haven't determined yet how much it's him, how much it's interactive, and what the relationship is between it and his other twitter account, llllll__lllllll
Short review: creative, fairly relentless use of unicode icons as a kind of latter-day ASCII art, veering between chaotic expressionism and tight renderings of cool skulls. On the hacking vs defaults continuum it comes closer to "Being and critiquing The People by using the tools made by The Man" than "Empowering The People by subverting The Man's power." Mostly it's jimpunk being jimpunk, but we're supposed to say it's all about the mix and avoid any suggestion that his art might be, gasp, gag, hermetic.
An article in the gaming journal Kill Screen didn't help much at all: the author started out with the fusty dichotomy of art-in-museums-you-aren't-supposed-to-touch vs wacky contemporary art where YOU are also the artist. She also uses the late '90s term net.art throughout. And apparently never doped out why jimpunk wasn't replying to her emails in complete English sentences similar to her own.
Unlike ASCII, which can be made on a typewriter, unicode depends on how well your operating system, browser, and or appliance can read it, so you may see a lot of posts like this one:
crashtxt also features screenshots of unicode arrangements, as well as screenshots of glitched versions of this and that. The twitpic at the top of this post is a screenshot saved directly from the site -- no idea how it's done or what the back story is, but it's an exquisite, or perhaps exq=.s.te image (despite being fuzzed out).
Addendum: As long as we're name-checking ASCII, let's also mention as precedent, the venerable, annoying "wingdings" or "webdings." On the crashtxt readability issue, here's a screenshot from Jules Laplace, who evidently can't see the unicode at all.