You could come and join us on Loose Canon at http://groups.yahoo.com/group/loose_canon/ We do get people coming along to use us as a resource and just posting canon questions.

You could if you wanted fix the oddity just by having them all say "I didn't know there were dungeons deeper than the Slytherin common room" rather than "...deeper than the Potions classroom".

The only other canon oddity I spotted in the story was that the scene where Snape interposes himself between the children and the werewolf is only in the film, not the book.