I'm hesitant to weigh in on this, because I'm pretty sure I'm not going to be attending any more conventions. (And you're about to find out some of why.) But what bothers me, as both a disabled and an organizational person, about what happened to Mari Ness at World Fantasy is not that they failed to have wheelchair access to her stage, the first time it happened. The temptation is to add "however many years ago that was," but you know, even this year. Sometimes you forget things, sometimes things slip through the cracks. Mistakes happen, and it's OK for them to happen as long as you admit they were mistakes and do something about it.
The problem is that they were unwilling to do that. They said "we're not going to get you a ramp," which, OK, maybe on some level the immediacy made that impractical. And then they said "we're not going to get you a ramp tomorrow either." Their solution to the problem was to make Mari and her fellow panelists come up with a work around for the problem on their own. And that is not acceptable, for reasons having nothing to do with disability specifically, and it is not something that can be fixed by demanding a policy on the thing that happened to go wrong this year, because something else is always going to go wrong next year, something you don't have a policy for yet. And then we end up in a cycle. People in this field already have a portfolio of policies they require of conventions, and pretty soon it's going to be a filing cabinet, because it's about putting bandaids on symptoms and not addressing the core problem.
And what if next year's issue is something that doesn't have a substantial, loud consitutency? Sexual harassment was going on at conventions for a long time before anyone actually started listening to the people being harassed and demanding that something be done about it. What is the thing now that sexual harassment was thirty years ago, that is harming someone and everyone is willing to blow off? (My own experience suggests that taking advantage of artists is one of those things. One of the things in my portfolio of policies that I won't be attending a convention without in the future is one where they pay their artists fairly.)
I want a convention which says "We will get you a ramp," whatever the equivalent of the ramp is that year, whether there's a social media constituency for ramps or not.
I want a convention which, when it unexpectedly makes a profit, doesn't decide to stick its guests with their expenses after enjoying all the benefits of a collaborative relationship.
I want a convention which, when it notices that it comped travel and rooms for some people for the same job other people were volunteering for and paying extra hotel for without any of those people's knowledge, apologizes and makes restitution.
It's not about accessibility, it's about responsibility. And I've come to the conclusion that if I want that convention, it's not going to happen in science fiction. Maybe I'm wrong. But I've seen enough of this cycle now, and I don't want to be in it any more.