When I have time I hope to set things down more clearly and answer the various questions people have raised, so it might be a good idea to wait until I've made that post before linking to it (as several folks have asked if they could do).
However, if you want to go ahead and link now, that's fine as well -- just so anyone coming here realizes that what they're looking at is basically me thinking out loud and working my way through the evidence in bits and pieces, as opposed to a well-rounded and coherent argument of the sort I hope to present later.
Thanks to everybody's who's thrown in their questions, additions, agreements and objections so far! I haven't had so much fun in HP fandom for a long time.
And now I shall be gone all day, so those waiting for more info will have to wait until Monday, I'm afraid. Sorry!