What if sometimes want auto-filling and sometimes don't? Necessary to keep manually turning on/off?

[Chris Seberino]

Sometimes you WANT auto-filling...sometimes you DO NOT.

e.g. When I am writing text like a comment in a program, I appreciate 
auto-filling.

When I want to squeeze as much in a single line in a computer program 
instruction
as possible, it gets in the way.

What is easiest way to have it both ways?  Must people keep turning it on
and off?

Thanks!

Chris