Reading more transcripts, I've learned that there is apparently an in-joke about implementing waylay as there is for xyzzy and various other magic words or unusual commands from old games... make it stop!

> waylay snape

You don your best highwayman's outfit and carefully conceal yourself around a bend in one of Hogwarts' many convoluted passageways, waiting in the shadows for your prey. At just the right moment, you strike, holding him at wand-point and demanding his Galleons or his virtue.

Unfortunately, it seems that Severus is an even warier creature than you had reckoned with. He appears only faintly surprised, as though he is used to people attempting to take him unawares and now half-expects assault at any time. Coupled with the fact that he is, in any event, a far superior dueller to yourself, it should come as no shock that you are quickly subdued.

You pick yourself up, humiliated, and dust yourself off. "Let that be a lesson to you, [player name]," he says. You can't bring yourself to meet his eyes.

As he walks away down the hall, blending back into the shadows himself, you hear his sneering voice once more: "And take off that ridiculous frock-coat!"