Fnord: I think part of my issue is my own attitude toward sex, namely that it's not something to take lightly. It has a lot of meaning and importance, and if people treat it like just another drug or buzz, all that depth is lost. Maybe AW is all about that loss, but you know sometimes one form of loss or another just cuts too deep or gets too personal and you don't want it in your game in that form anymore.
Simon: that's a good point I hadn't thought of before. If we're roleplaying at the level of language, then we can introduce our characters' words directly into the fiction, and see what meaning it has right away because it's all just language, but when it comes to physical actions like kissing, obviously we're not doing that at the game table, just as we're not actually acting under fire or seizing by force at the table either. So we need a move mechanic to help us decide what the fictional effect of these things should be, because whatever's actually happening there can't just be demonstrated in an obvious way that everyone can immediately agree upon at the table.
Vincent, maybe that's why your gut says the act should be specific and concrete. It's about modeling something we can't actually see or do.
Incidentally, that's an essential purpose of conflict resolution systems, too -- to help us model conflicts between characters that don't actually exist between players. If characters agree, we all know what to do, because the players agree too, but when the characters disagree, we can use a system to help us work it out.