I like the idea of A/B testing of titles. It would be nice if Medium provided an easy way to do that, but I doubt it's on any of their project whiteboards, much less in development.

A/B testing has a long history in software. The idea is to post two (for example) sets of changes to a beta test site (again, using a website as an example) and see which gets the best response.

You could actually do that on Medium by posting two "same" articles, with different writing approaches and headlines addressing the same topic and presenting the same talking points. That would be an interesting experiment.