IRC (or XMPP) is not the only answer to open standards based communication these days — we’ve been building Matrix.org as a non-profit open standard for powering Slack-style communication services which are entirely open, decentralised and interoperable, with no single server or service controlling or owning the conversation history. Matrix also provides bridges through to existing services like IRC, Slack, XMPP, Lync etc in order to liberate conversations from being stuck in any single vendor silo and basically matrix everything into one great big meta-network.
There are now a whole bunch of open source clients, servers, services and bridges which implement the Matrix standard, and one of the really cool things we’ve seen are contributions from the wider community for stuff like accessibility in the clients. For instance, Vector.im is a glossy open source Matrix client which apparently works pretty well on screen readers thanks to stuff like https://github.com/vector-im/vector-web/commit/9153efd3. And alternatively one could just use (or write!) an alternative dedicated accessibility-focused client if needed, thanks to the open & standardised APIs.
(Sorry for the plug, but it seems rather relevant to the post!)