Oh, my. There are so many things to praise here (the praise could easily go on for more words than the ficlet), but let me begin with how tight and perfect your phrasing is:

When the clothes came off and the lights stayed on, Snape smirked and his partners often fled if they were beautiful. .. .

Easy enough to take him bent over a desk, the wooden leg thumping into the floor with the rhythm of his thrusts.

That is just gorgeous phrasing. Polished and taut.

And you give a very fine demonstration here of how depictions of sex can further and deepen characterization. Because this is a character study, done with grim humor and intelligence. Wow.

Thank you. This is really unlooked for, and so deft. What a lovely present!