Firstly, I've never been sure how Highlighting was really supposed to work. For example, maybe the Battlebabe's low Hard is something that interests me - she's not actually that tough, just cool. But if she's taken the right move, she'll never roll Hard unless there's a custom move in play that lets her - so am I being a dick by highlighting the stat that interests me but she can't choose to focus on? That seems worse in 2nd ed, since there are more chances to simply overwrite one stat with another - the Battlebabe can roll Cool for all Hard moves on the sheets, the Gunlugger can do the reverse, etc.
Highlighting a stat that someone *never* uses because of substitution is, yeah, usually a dick move; it's good form to ask the subject if there are stats they don't use. In 1e, it's not *totally* uncool to tell an Ice Cold Battlebabe to highlight hard; it means you want to see them try (and maybe fail) to Seize by Force. There might also be custom moves in play that aren't subject to stat substitutions; if the MC expects those moves to be relevant in a session, highlighting accordingly is okay.
Secondly, doesn't that mean that there's a double incentive to take the stat-swapping moves? It not only lets you use a much better stat, but it means that if the good stat is highlighted, you'll get a lot more xp out of it. And if it is a dick move to highlight someone's swapped-out stat, that also means they are more likely to have the good one highlighted - there are less options for the other players to pick from.
Yeah, all true.
And thirdly, now that manipulating a PC can strip highlights off them if they don't go along... that seems like a weird incentive to me. Firstly, towards the end of the session it becomes less meaningful since there'll be less chances to roll left. Secondly, if you refuse to be manipulated twice, there's no longer any penalty for refusing since you're out of highlights.
I haven't seen how it plays out yet, but I really like the highlight-removal stick on Seduce/Manipulate. It's symmetrical with the XP-awarding carrot now, and much more clear in application than the "acting under fire" penalty of 1e. You're correct that the "weight" of it changes over the duration of a session.
If a PC is refusing manipulation-with-stick repeatedly, well, they're clearly a stubborn individual. Seems like a person who's stubbornly saying "no" repeatedly ought to find it easier and easier, while learning less and less. ;)