Rate quality/simplicity of each lesson
Perhaps as a way of allowing users to provide feedback on lessons, could we rate each lesson's quality/simplicity out of 5 stars or something after completing it? That might provide some feedback as to which sections need more polish.
For instance, I was working through "French: Verbs: Infinitive 3" and finding many errors, weirdly translated sentences, etc. It was long, problematic, and discouraging. It'd be nice to be able to flag these entire sections in some way.
Of course, if you're already tracking error rates per section/lesson/sentence, then you already have those analytics or something that approximates them. If so, could you expose them in some way? It'd be nice to know if a problem is just me or not.