Van Halen famously had a rider on their touring contract that stipulated there must be a bowl of M&Ms backstage -- with all the brown ones picked out. But despite appearances, this wasn't ego run amuck. That contract rider also had complex technical specifications for electrical systems, clearance, even how much weight the girders must be able to support.
Once Van Halen arrived to set up a show, any brown M&M was a quick red flag that the venue hadn't read the contract carefully, and so probably wasn't complying with those detailed technical requirements, either. And while a brown M&M might not be poison, those technical requirements were literal showstoppers. Electrical fires are not rock 'n roll.
This brings me to accessibility policies, and more specifically to Mary Robinette Kowal's pledge not to go to a convention that lacks such a policy. Seriously, stay with me.
Some years ago, John Scalzi made a similar pledge regarding harassment policies. At the time, I worried that participating would be damaging to my career -- when you're a tiny fish in a wide blue ocean, you have to take all the publicity you can get your grubby mitts on.
I've been to a lot more conventions since then, and here's what I've learned: the sort of convention that can't be bothered with a harassment policy is likely going to have serious organizational problems, weird politics, dull programming, or some combination thereof. It's true I'm very early in my career as an author, and I can't afford to miss out on promotional opportunities.
But the flip side of that is that as an early-career author, I pay my own way to conventions. I have only so much time and money to give, and there are so many, many conventions. So I need to budget carefully to make sure I get the most bang for my promotional buck. I really can't afford to go to a lousy convention.
Which means harassment and accessibility policies are increasingly important to me -- not just because they're morally right, not just because of my leftist SJW politics. Even if you're not worried about harassment yourself, even if you're not worried about accessibility yourself, if those policies are missing, that should be your brown M&M. The sign that what you're dealing with is very likely to be a shitty convention.