I really like the substance of your tutorial, but even as someone with 15+ years of bioinformatics and programming experience, it is sometimes difficult to follow the string transformations in the BWT section. Would it be difficult to break down that section further into sub-sections? For example, it looks like the suffix array part is a tangent, as you switch to what BWA does and there on out, the suffix array part is abandoned. You may want to add the SA part as a side note then, and explain what BWA does, then take a break at that point before jumping into recreating the original sequence from the last column.
Plus, I think you run into a language barrier of some sort at the reversible transformation part, as your explanation doesn't really make sense: you use the concept of "columns" as a foundational block but you haven't introduced columns at all until that point, and while trying to figure out what you mean by columns, I've lost track of all I've kept in mind about the BW transform so far. The end result is that I read and re-read until that point and then stop because I can't figure out what's going on.