Things that bother me in the extreme: Not showing letters as they are typed in the advanced lessons. That immediate feedback is how I know that I'm typing a word correctly and how I know if I make an error that I have corrected it.
Penalization for adding additional whitespace between identifiers in some situations: "[one,two,three]", for example, I personally like adding a space after the comma and do it automatically.
Are the typing mechanics different in latter/advanced lessons? If so, it's something I need look into. Or is this a different problem?
I preserved the whitespace the project authors used. I'm a little picky too regarding these details, but I want users to see code in its original form.
Penalization for adding additional whitespace between identifiers in some situations: "[one,two,three]", for example, I personally like adding a space after the comma and do it automatically.