So, because you can't deviate below the x axis this is really that much less useful?

This also doesn't meet the high resolution part of Tufte's definition ("a small intense, simple, word-sized graphic with typographic resolution"[1]).

[1]: http://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=0...

They're comparatively higher density...

This gives you eight levels (plus blank)[1]. Most of the type I read is at least twice that many pixels high.

[1]:https://github.com/holman/spark/blob/master/spark#L46

Tufte honestly thinks pixelated type is pretty terrible, too. 16 pixel density is embarrassing compared to printed or pressed text.

But in either case, it's obvious that's a silly argument. Trends posterized to 8 levels are far easier to read in "sparkbar" form than as a list of numbers. It's suboptimal, but better than the plain list.

You must admit the horizontal resolution is quite low as well