Tried it on the slow 3g preset in chromium for the Cory doctorow tweet linked above with cashing disabled (as a first load would be).

20 seconds load time - though readable before that. But you don't want to do that on a metered connection.

This is true, but I also don't think anything but a tiny fraction of HN is on a slow connection.

And? Do people who can't afford a fast connection not deserve to read quality content?

I think the number of people who want to use twitter, refuse to install the twitter app for ideological reasons to save data, and also have a very slow internet connection is a small group of people, yes.

It's more about people who don't want to use Twitter, but want to be able to read random posts linked from link aggregators and blogs.