Few things I like in IRC over Matrix, or any other protocol in professional setting:

1. Does not try to blend #security and #decentralization. By not having security at all is one way to implement a sound security model. This allows to design security properties both by means of infrastructure security, i.e. outside the protocol, and also by tunneling, i.e. inside the protocol (classic example is off-the record messaging). This keep the core protocol compact and sound, and easy to verify for correctness, which is by itself a strong security property.
2. Has both decentralized and client/server based topology since 1988(!). It is a network of servers, which together form an IRC network.
3. Protocol messages are both rigidly structured AND still human-readable (unlike JSON), and have a clean specification (RFC 1459).
4. Features not in the protocol itself can be implemented efficiently with bots, given the ease parsing and producing IRC protocol messages.
5. IRC network heals fast from failures and has high #availability properties, given the clean and rigid definition of what it does and what it does not do.

#IRC #infosec