Palinopsia is fickle, she reacts to what you say. She'll probably pull up her skirt again, don't worry!
Good catch on Fleur not updating her rumour part, will fix immediately.
Clues for the sewers are near the wall and the barracks, heard from different sources. The alleys mention the south part IIRC.
And yes, that alien code cryptography puzzle is way too hard, with only a small hint from MxI to help out. I'll probably soften that considerably up in a later update, but for now I'll cave in and give the solution (try and figure out how to come to that then instead
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Spidersilk has no use yet, it's there for the next major update.