In the space you use for editing a single file I can fit four 80-column source files (which I do, I also have a giant monitor).

Also, excessive nesting is almost always a code smell.

I think the issue with a very long line is akin to writing without punctuation because code is usually much more information dense than prose it becomes hard to follow what it is supposed to mean than if there were pauses for you to consider points in isolation but otherwise I don't see a problem with long lines if you have for example some very long silly OOP getter chain which is essentially one expression as for tons of nested blocks the general argument is it's a hint that your single unit of base indentation is doing too much and there is possibly something to be done about it though like everything it is usually taken to a unhelpful extreme.

I suspect nested loops going that deep are very likely to be a design problem.

Loops nested deep enough that you need an ultrawide to avoid truncated lines!?

The idea of 350 characters worth of nested loops leaves me speechless.