I'm not sure what you mean by saying that "Two column layout is a relic of a single page layout". Columns have a long history (newspapers come to mind) that does not seem to be tied to single page layout.
The most important thing that columns preserve is readable line lengths. If you want to maintain good, readable line lengths on the web, you are going to end up with a relatively thin column and a lot of scrolling. Multiple columns allow us to more efficiently use the visible on screen space while maintaining readability. That seems pretty valuable to me.
Agreed. The column and optimal line length conventions of print weren't arrived at through whimsy, but rather a centuries of experimentation in improving readability. Obviously screen is a very different medium, with it's own unique considerations but optimal line length is just as important a readability issue as ever.
> The most important thing that columns preserve is readable line lengths.
A single column can give you that.
Multiple columns seem to me to be fundamentally incompatible with (vertical) scrolling. Yes, they make perfect sense when your pages are fixed-size, and the entire page is visible at once, but when you have a single page of potentially unlimited height, where do you break one column and go on to the next?
A possible solution implementable by a client:
Have the second column be position: fixed; until you scroll to the end of the 1st column - only then start scrolling the 2nd column (and so on to the 3rd column).
I find multiple columns in pdfs very annoying to read as you have to scroll down to the bottom of the page, then back up to start the 2nd column, then scroll down to reach the end of the 2nd column.
I believe scrolling is not ideal. You van break your text on viewport-height and then put as many columns on the screen as possible. This drastically reduces the amount of scrolling required.
I've tried that but it comes out feeling kind of weird. Also, most people don't have a pointing device that allows for horizontal scrolling. But it is totally workable.
The most important thing that columns preserve is readable line lengths. If you want to maintain good, readable line lengths on the web, you are going to end up with a relatively thin column and a lot of scrolling. Multiple columns allow us to more efficiently use the visible on screen space while maintaining readability. That seems pretty valuable to me.