ep6: Do not use subheadings -- really?

In [episode 4](http://carpentries.github.io/lesson-example/04-formatting/index.html) there is a recommendation not to use sub-titles in episodes.

Perhaps it's a wording ambiguity, but that very page (and indeed the whole lesson example repo) makes extensive use of subtitles - and to good effect; breaking the prose up into navigable chunks. However, no justification is given for this recommendation.

[I was proposing](https://github.com/swcarpentry/matlab-novice-inflammation/issues/150) to use some sub-headings in the MATLAB lesson, and hence this discussion.

I think it will make the lesson material easier to teach and easier to follow for learners.

What are the current thoughts on this?