Thanks for all the comments so far. I know Coda isn't designed as a blogging platform but I liked being able to directly connect the interactive charts. It's better on desktop than mobile. That said, I did spend quite a while copying it over and reformatting it for Medium this afternoon - there's a link right at the top - just in case people didn't want to deal with Coda!
I would have liked to make the charts a bit clearer but the customisation in Coda is quite limited. Nobody I showed it before posting it on HN had any complaints. I can add some more context to the bits that aren't clear.
As for how long I spend tracking my time... not too long really? I've been tinkering with my document here and there as I go, and now generally I just switch to the right project and hit "Start activity", pressing "Save" when I finish. I've been using Coda rather than bootstrapping (yet another) private time tracking web server because it provides a different sort of agility to what I'd get if I was programming everything myself.