An express design goal is to not bake in assumptions about an editor. Programmers really like their editing tools. I've lived through the waves from vi to Emacs to vim to Sublime Text to what-have-you. We'd really, really like to make the language pleasing to work with without depending on an editor (indeed, each of us seems -- perhaps by accident -- to be using a different editor for Pyret, which may be influencing our decision).
When editing/copying, it's not typing skills but editing skills, which are arguably subtler and even harder.
Your point about programmers having favourite editors (which I consider valid) contradicts the point you made about an important part of your audience being middle/high schoolers, which I don't think have such strong preferences towards one editor or another. It seems to me that you are making compromises to cater to the needs of an audience which is much broader than that you have identified for the language.
It would be a shame to compromise the design of an interesting language just because the target audience is not clearly defined.
I have many target audiences. I mentioned middle- and high-schoolers in response to various other questions, but I don't anticipate them being the largest audience. I expect the biggest audiences to be introductory college-level education and second/third-year courses on "paradigms" (blecch) that want a flexible language to illustrate several concepts. Finally, I am also consciously building a language and book to appeal to the working programmer who has not learned to think of computation as primarily producing values, and would like to quickly get up to speed with that idea.
All of these are educational audiences. I don't see how one can define the audience more clearly than that, given that I have no control over any of these audiences.
When editing/copying, it's not typing skills but editing skills, which are arguably subtler and even harder.