Are there forum-like collaborative Q&A/Annotation tools out there? I’m teaching an introductory programming course using the Moodle platform and I find that the forums are not used as extensively as they could be. Especially, students ask duplicated questions, have a hard time formatting their code correctly, and don't organise their questions and answers in a very structured way (e.g., they ask a new, unrelated question using the “Reply” button while reading another question).

I would be greatly interested in a web-based tool that would allow me to do this: divide my window vertically into two large columns. In the left column, I could post code snippets, my slides as PDFs, my exercises as PDF or HTML online, etc. In the right column, student could ask contextualised questions related to a particular line in the exercices or in the slides. The advantages would be:


All previously asked questions related to this same point would already be shown on the left. This would considerably lower the the probability of duplicated questions.
While asking a question, no need to copy and paste a code snippet to inform the reader about the context — the context is shown right there in the left column.
A voting system similar to the StackExchange system would be great.


Are there any such tools out there?
This is likely my shortest answer ever. 
Check out NB (formerly "nota bene") via MIT
 http://nb.mit.edu/welcome

Instructors upload pdfs and students can highlight particular sections of it and ask questions.