I would tone down the purple bracelet to "the wearer may at all times be presumed to be open to all offers of intimacy or informality which are permitted at the gathering, but their refusal of specific offers is still to be taken seriously".
Would this system require that the level of intimacy and informality for a gathering be made explicit?
I imagine that one would post some kind of notice at the entrance to the venue, which would precisely explain the mapping of bracelet colors to the norms of personal interaction that they indicate; the bracelets themselves would then be piled up in baskets beneath that notice.
I think it's important to have explicit norms of permissible behavior for a few reasons:
The juridical function of explicit norms: Explicit norms form a bright line by which to identify malicious actors, such as, for example, an aggressive pickup artist who is willing to harass dozen
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)