I have a couple more now!

1) how come sirius was able to get his head into the gryffindor fireplace. Actually no, why wasn't the Gryffindor fireplace watched when he was known to be on the loose?

Then, why was he able. It seems foolish to place so many wards on a school and BAM someone can just come in the fireplace.

1.a) Imagine McGonagall a married witch. Her husband (idk Thomas McGonagall or something) waits for her to come back from school every night (through the fireplace in her office obviously) and mends her tartan robes while she sips a brandy and regales him with the latest school gossip.
(okay, so this was just me imagining, but ARE all the professors so chaste?!)

2) the spells are latin because of some influx of magic development during the Height of the Roman Empire. Obviously spells do not have to be latin (see Point Me, waddiwasi, riddikulus) Perhaps enough 'major' spells were perfected then (discovered, whatever) and then whatever came later was just named in Latin because those people were stuck up prigs that wanted to stick to "form".

Misc A) Lupin forgot to tell Fake-Moody that his class also studied vampires. ?!!!!!!?!?!?!?!