Slack actually has a really good IRC bridge that you can turn on, allowing IRC users to connect…
Simon Willison
32

I’ve heard screen reader users say that the IRC bridge sends _too much_ information over the line; it’s too much noise. I haven’t tried, so can’t really say. At the a11ySlackers channel we use sameroom.io to link Slack to Gitter (which also has an IRC bridge). Works very well.