In reply to Steve Pheriche.

I see that 10up recently carried out some usability testing with results HERE. That’s interesting but it polled just five participants.

I'm really excited about the work that Sarah has been doing in Gutenberg! This article might help shed some light on why 5 users were chosen. In short, when conducting user tests, you can use as few as 5 users to uncover 85% of usability problems.

This helps to greatly lower the barrier of entry for conducting tests, and then conducting followup tests based on changes you've made.