[seanmcdirmid]

80 characters is nice for side by side buffers. Also, lines that are too long horizontally are difficult to scan (especially if they are much longer than the lines around them) and can benefit from some work on vertical layout.

[pizza234]

How much time do developers spend on side by side buffers?

I get the difficult to scan point (although I find it subjective) but the side-by-side argument is optimizing for a comparatively small use case.

[YorickPeterse]

    > How much time do developers spend on side by side buffers?

In my case: all the time. On my desktop (which has a large display) I often tend to have 3-4 vertical buffers open. Being able to fit all my code in those buffers is a godsend.

[3pt14159]

I know this is a bit of a rare condition, but I have very sensitive eyes, so I need to work on a single small laptop screen with decently large font size, otherwise I get eyestrain and I'm out for a week. So when I have two emacs windows open even 80 characters wraps around. I put up with it, but when a codebase has something like 70 or less characters per line I find it much easier to develop in.

[Deradon]

It's my default. On the left buffer I've got the implementation, on the right buffer I've got the spec/test.

[endgame]

It's my default mode of working. Even in a statically-typed language (I mostly write Haskell these days), I often have one buffer for the things I'm working on, and 1..N buffers of references or parallel changes.