I think the author has a point .. however we're all conditioned now to the standard-ish font size on the web. We all sit at a distance from the screen optimised for a particular size - and as most sites are about the same we zoom in or our a little. Changing that is just jarring.

The number of characters per line is, however, important. I tend to either resize my browser to narrow sites like HN or use the 'Instapaper Text' button to totally transform the page.

One things missing in this article is talk about line-height. The longer the line of text and the longer the paragraph, the more line-height you need. The white gap between the two lines helps the eye to find the next line as it quickly scans back to the start.

Many news sites still use a small line-height reminiscent of newspapers where whitespace is expensive. I think the designers think it gives the feel of 'real' news.

TL;DR: lines around 70 - 80 characters are good. But more important is sufficient line-height to scan back to the start of the next line instantly.