When I was younger, my own feelings were the main social signals I relied on to help me navigate relationships. My own feelings of sexual attraction seemed to mean "maybe there's a potential romantic relationship developing between us." Anxiety seemed to mean "maybe these people don't like me, or maybe this person's angry with me." Shame seemed to mean "maybe I have done something wrong."

And this isn't crazy! Social feelings are often at least partially the result of how we relate to each other. The idea that "I am attracted to you because you're doing something on purpose to make me feel that way" is a really problematic idea, but also this is a real thing that happens. People do try to kindle feelings of attraction in each other. The problem is with attaching justifications for one's own bad behavior (i.e. ideas of "asking for it").

As I matured, I started doing something slightly more sophisticated. This was reading signals of relationship into conscious behaviors. If a woman I was friendly with invited me into her bedroom for a non-sexual reason, that might be a signal that she was sexually interested in me. If somebody didn't show up for my birthday party, that meant they didn't like me, and if they invited me to an event, it meant they did. A person who smiled at me when we saw each other probably liked me and wanted to be friends.

This was definitely better, not only because it was more accurate, though far from perfectly so, but also because it led me to be less reactive to my immediate emotional state. Feeling anxiety no longer also meant "I have to fix this relationship rift." It just meant "I need to take care of my discomfort."

At this point in my life, I still use implicit signals, but I recognize them as poor-quality evidence that's mainly only useful for navigating life in the moment. If I have a tense phone conversation with my long-distance partner, I'll make it a point to have a "relationship repair" conversation later, just to be on the safe side and keep mostly happy vibes between us. But I don't assume that just because the call was tense, that there's some anxiety between us. I have plenty of evidence that sometimes, an apparent calm is masking real tension, and apparent tension is from something else entirely.

So what I lean on a lot more are explicit signals. I will tell people in no uncertain terms things like "I really enjoy your company," or "X makes me feel frustrated," or "I'd like to get to know you better."

I might start thinking of this as Portable Tell Culture.

Logan defines Tell Culture as:

1) Tell the other person what's going on in your own mind whenever you suspect you'd both benefit from them knowing. (Do NOT assume others will accurately model your mind without your help, or that it will even occur to them to ask you questions to eliminate their ignorance.)

2) Interpret things people tell you as attempts to create common knowledge for shared benefit, rather than as requests or as presumptions of compliance.

I think there are significant risks associated with many "tells." I think the Kelly model of betting is appropriate: you're trying to maximize the "growth rate" for your life satisfaction through a series of positive-EV bets on "tells," which often have basically a "success" or "failure" outcome. In this model, some "tell bets" are inflexibly oversized, putting the teller at risk of ruin even if the expected value is positive. In those cases, you should not tell the other person what's going on in your own mind.

And of course, you don't always have the opportunity to declare "tell culture," and where it's not for-sure operating, you sometimes would be most accurate in interpreting "tells" as requests or presumptions of compliance. Certainly, you can't expect other people to interpret your own "tells" as mere "tells," especially if you are a high status person. I suspect keeping these two principles in mind would prevent many a sex scandal.

But in Portable Tell Culture, the focus is on taking appropriately-sized "tell bets," given a context in which there's a real but acceptable risk they'll be misinterpreted as requests, presumptions of compliance, and so on. I jump between many social settings, and I wouldn't trust a full "Tell Culture" to be real and consistent and durable, even if its participants claimed it was - and I would find it confusing or risky to switch in and out of that mode. 

But Portable Tell Culture is something I can take with me everywhere I go, and I find that it makes my life work better the more I lean into it.

How do we communicate that sexual abuse is really not ok, without making victims of it feel like it's worse than it actually is?

I'd distinguish between the seriousness of the crime from the suffering of the victim. I think that this distinction is common sense. I agree with you that they are sometimes conflated. It seems like you could communicate this with a message structured somewhat as follows:

"C is a serious crime. Victims of C may suffer X, Y, and Z as a result. Not all victims of C experience these consequences, and it is important to let the victim of C decide how it affected them."