> When IRC federation breaks, everyone can see it, except for the rare people who aren't in a shared channel with anyone on the other side of the break.
Well sure, you could see that something was going on, if you were paying attention. But how does that solve the problem? Does your IRC client stop you from sending messages if it detects a netsplit?
I don't think IRC is a good analogy here because there's no "message resync" that happens when the netsplit is resolved. If there are two people on opposite sides of a split, and they both send messages to a channel while things are still split, they will not see the other's messages when the split is over.
In the Matrix case, if a homeserver disappears for a while, it will sync any missed messages when it comes back online.
Well sure, you could see that something was going on, if you were paying attention. But how does that solve the problem? Does your IRC client stop you from sending messages if it detects a netsplit?