Which bit do you find challenging?
I mean, I was kinda being snarky (I don't think what I suggested is all that hard or unusual at all, though it obviously varies. I've noticed a few reasons for that:
-The person is failing to model the other as an agent, as a center of perspective. Their model of the person starts and stops at their own feelings and reactions; hence, if they find the person attractive, "X is attractive to me" becomes way more salient than it would otherwise be, in determining how they'll attempt interaction. Men do this to women a lot, in general, but there are plenty of other dynamics or situations which can lead to it. Autism or similar psychological variance is massively overstated as an explanation for it; it's way too prevalent a behavior in the general population for that.
-The person has no sense of whether something is appropriate or not, even though they've modelled the other party accurately ("is agent, has preferences"). This is very common among people who, for whatever reason, have had socialization issues. They usually know there's a bewildering array of possible rules or at least broad patterns that might theoretically bear on the answer, but it's not obvious which ones apply, or that they haven't even thought of. To be honest, even socially-successful people sometimes have trouble navigating that, as soon as they're in circumstances that are unfamiliar to them -- another culture's norms, or when dealing with a known charged dynamic and they're concerned about signalling and how they come off. The trick is that there's usually not any one right answer; it can be as specific as the nonverbal communication between two parties. Is asking for a hug creepy or unnecessary? Sometimes, if you can't read the cues, you really can't know short of asking. This means there's always some subjective sense of risk; the problem is they don't know how to calibrate that to the situation, don't have a model of likely prior probabilities. All they really have is a sense of the variance on the options, which is incredibly wide.
-They're failing to not-assume-yes. This is related to the first problem; the person is failing to be aware of, or consider, the pressure their request creates, or is equivocating the risk of being told "no" or declared "creepy" to be symmetrical with the worst-case scenario on the other person's chart. For one reason or another, it just seems to them that if there's no obvious reason not to, no compelling objection in particular, then obviously the thing they want should happen. "No" isn't heard as a good answer in and of itself, not a sufficient report of the other party's preference; it's felt as somehow keeping them at arm's length, denying them the information they need to know how to get what they want. This sort of thing is very obvious from outside, because it leads to different behaviors and responses, and body language tells, when confronted with a "no."
Your last paragraph is excellent. (Others also good, last excellent.)
One of the lessons highlighted in the thread "Less Wrong NYC: Case Study of a Successful Rationalist Chapter" is Gender ratio matters.
There have recently been a number of articles addressing one social skills issue that might be affecting this, from the perspective of a geeky/sciencefiction community with similar attributes to LessWrong, and I want to link to these, not just so the people potentially causing problems get to read them, but also so everyone else knows the resource is there and has a name for the problem, which may facilitate wider discussion and make it easier for others to know when to point towards the resources those who would benefit by them.
However before I do, in the light of RedRobot's comment in the "Of Gender and Rationality" thread, I'd like to echo a sentiment from one of the articles, that people exhibiting this behaviour may be of any gender and may victimise upon any gender. And so, while it may be correlated with a particular gender, it is the behaviour that should be focused upon, and turning this thread into bashing of one gender (or defensiveness against perceived bashing) would be unhelpful.
Ok, disclaimers out of the way, here are the links:
Some of those raise deeper issues about rape culture and audience as enabler, but the TLDR summary is:
EDITED TO ADD:
Despite the way some of the links are framed as being addressed to creepers, this post is aimed at least as much at the community as a whole, intended to trigger a discussion on how the community should best go about handling such a problem once identified, with the TLDR being "set of restraints to place on someone who is burning the commons", rather that a complete description that guarantees that anyone who doesn't meet it isn't creepy. (Thank you to jsteinhardt for clearly verbalising the misinterpretation - for discussion see his reply to this post)