[Chris_Newton]

Yes, the ideal ("most legible") width for a column of text is ~60 characters, no question.

We can reasonably question what makes a good line length as well.

You have to define what you’re trying to achieve first. For example, a line length that is subjectively pleasing to readers in a certain context might not be the same as a line length that optimizes measured reading speed or retention.

Once you’ve done that, differences start to emerge. During research studies, readers have often preferred shorter line lengths (typically around 40-50 characters) over longer ones (say 60+). However, in terms of reading speed, lines as long as 100 or so characters have sometimes resulted in better measured performance. Please note that I’m oversimplifying horribly here, both ignoring established confounding factors like font and line spacing, and ignoring context such as screen vs. print or paged vs. scrolling presentation.

So, while the old rules of thumb like “two alphabets” seem to be reasonable starting points, we shouldn’t assume that they are optimal in all cases.