Does this work?

[CountVanBadger]

In the XNPC chapter I'm writing, Jeremy is talking to a shop owner who's a higher level than him, and he's using a skill to try and get Jeremy to buy something. The skill works by imbuing power into a word that grabs the attention of whoever hears it and keeps them from thinking about anything else for a few seconds. I get this across by making the word he imbues the skill into bold, but I don't let on exactly what's happening for a while. I'm hoping people will notice the bolded words, but not know what they mean. Then when Jeremy finds out what's happening, they can go back and go "Oh, those must be the words he put the skill into!"

Does it work?

Jeremy’s eyes widened when he realized exactly what he was looking at.

“You…” he said slowly. “You’re not an NPC!”

Raphael gave a modest nod. “You flatter me, sir. Is there anything in particular you were looking to purchase today?”

Almost immediately, the fact that he was talking to another sentient human being was chased from his mind, and all Jeremy could think about was the wall of books looming over him. What felt like every fantasy he’d ever had as a child came flooding back into his memory. Could Raphael’s books teach him how to breathe fire? Shoot lasers from his eyes? Could Raphael teach him how to fly?

If brains could drool, Jeremy’s would have been dribbling out of his ear and onto the floor.

[...]

“As we were speaking, I couldn’t help but notice that your level was rather, ah, low,” Raphael said apologetically. “I hope you’ll forgive me for prying.”

“Yeah, no problem,” Jeremy said absentmindedly, his attention still on the books they were passing.

“Am I correct, then, in assuming that this is your first time picking out new skills and spells?”

“Uh huh.”

“Then would you like a brief explanation of how they work?”

“Sure, I g…” Jeremy’s voice trailed off as he felt his eyes be drawn back toward the bookshop owner. He wasn’t sure what it was, but something about what Raphael had just said demanded his attention in a way that was impossible for him to ignore. “Uh, yeah, that’d be great. Thanks.”

[...]

They ventured down yet another aisle, and a particularly large black book with silver script caught Jeremy’s eye. He frowned at it. Unless he was mistaken, that was one of the books that had been on the first shelf he had looked at. Was Raphael leading him around in—

“There is no true limit to how many you can learn, except for your own MP in the case of spells,” Raphael said, drawing Jeremy’s attention back to him.

 

[Arkus86]

It is rather obvious the bolded words are emphasized for a reason, and it should not be difficult to connect the words to the effect they have, even if you don't explain outright what is going on. In that sense, I would say it works.
My first thought would be some form of compulsion to do what the words say, which... does not sound entirely accurate from your description and would not work with the last example, but if that's the case, it makes me question whether the choice of which word to imbue is arbitrary, or if it has a purpose other than timing.

 

[Time4T]

The idea of magical subliminal advertising is cool. Since your question made me forewarned, I already knew what I was reading. So I'm not sure if I'd have figured it out from the excerpt offered alone. I think at least a vague sense that Jeremy feels something of the emphasis would help make the connection. If you're going to explain the compulsion after the fact, am I going to want to go back and reread? I hate having to go back and reread.