Just from a personal POV, I find lines over a certain length to be very hard to read, in part because paragraphs tend to disappear, and because of the long travel distance to the beginning of a line. Generally, line length makes a huge difference as to my comfort while reading. Reading the linked article, 50 cpl is too small for my comfort, while 95 cpl was getting to be too long.
But other factors matter, e.g., intraline spacing, font, what else is on the screen.[/qote]
There are basically two different factors at play, one argues for a short line, the other for a long one. 1) how often your eyes have to follow a line break (the less often the better) and 2) whether you can follow the line (if you can't see both ends of the line at once, your ability to follow it is degraded).
There are, then, other factors which will enhance or degrade (2), as you note. And it will vary from person to person. But all I needed was to dispel the "short line is flatly better" point.
Does this mean my ridiculous run-on sentences are actually fine? If so, YAY!
I am pretty sure poor punctuation and structure will degrade comprehension and reading speed, though I have to admit this was outside the scope of the study I referenced above