[pmontra]

Most of the times I use less in the terminal. Or vi, it's not easy to accidentally make a change and save it. Or the browser in GitHub, Bitbucket or what else hosts the project.

I write code with emacs. I could turn a file in read only mode but I prefer not to mix what I'm working on with what I'm only reading.

[OrderlyTiamat]

Have you considered turning to the dark side? You can have vim keybindings in emacs with evil, so you can stay in the normal state like in vi, so accidental changes should than be caught identically as in vi.

But I guess having different tools for reading and writing is valuable in itself, too.