this is a difficult thing to have conversations about because it provokes really strong reactions in people for completely valid and understandable reasons, so please feel free to hit da bricks on this post whenever you want, but I do want to try and analyse the jonmartin slaps. we get three across 160, 169, and 172, and a line addressing it in 173, and then it never happens or comes up again. none of them come out of nowhere, and they mostly fly under the radar until 173 because they all broadly fit the "slapping someone out of a trance in an emergency" trope, but each of them slowly decreases in urgency.
the first time, the apocalypse starts up and martin comes back to find a passed out jon, can't wake him by making noise, and strikes him in a panic. this makes sense, this is a man who has entered a supernatural coma before and martin had no idea what was going on, so of course he'd jump to something desperate.
the second time, they're in a burning building, jude arrives while jon is still mid-statement, and when making noise doesn't work martin slaps him out of it. this makes sense, they were there for jude and if jon didn't come back to himself then she likely would have hurt them, though martin knew that her powers against them were limited.
the third time, jon is getting pulled into into a repeating statement instead of coming out on his own like usual, so martin speaks once or twice to try and get his attention, and then slaps him out of it. this... again, it makes sense, jon was getting trapped, but there was no immediate peril like before, martin just got freaked out and wanted to leave quickly. he seems to get that it was harsh because he apologizes for it, but they don't linger at all, martin just starts in on them having to leave immediately.
the last time it's mentioned is when they're on night street, during what is one of their most intense arguments. jon tries to talk about the suffering of the children there for longer than he needs to in order to make a point, martin cuts him off, and he pointedly says, "thank you for not hitting me this time." it never happens or is brought up again.
to our knowledge, jon doesn't say anything about the slapping until 173. he's not a guy who's known for speaking up when things upset him, he was amiably working with daisy within about a week of her trying to kill him, so it makes sense that he would just sit with this comparatively more minor thing. however, I do think it's relevant to note that, at this point in their relationship, martin will sometimes voice his feelings and boundaries (not listening to statements, not consenting to mind reading, worrying when jon expresses discomfort with his body), while jon doesn't. from the couple of times he does talk about his feelings this season, I think that tendency comes a few places: he has a hard time being aware of his emotions at all, he doesn't know how to evaluate his emotions' importance in comparison to others', he assumes his emotions are obvious and thus people already act with full knowledge of them, and the topic is just hard to make himself talk about. from what he says in 173, I think the slaps bothered him the entire time, but he made himself be fine with it until he was upset with martin for unrelated reasons and finally let it out.