It's fascinating to watch someone code in an environment so different to the one I'm used to (vim, no highlighting, no formatting, no realtime errors or lints).

It's fascinating to watch someone code in an environment so different to the one I'm used to (vim, no highlighting, no formatting, no realtime errors or lints). What's more important though than any of these is to have such a great grasp of the code that the author can talk through everything. That's a great exercise no matter what environment you have.