Like I was saying, IRCv3 has support for replaying the channel's history, as long as it's stored serverside. But I don't know if anything actually implements it, even IRCCloud which is v3-compatible.
At the moment if you join a channel you can't read its backlog, no. They could implement it though if they used logs from their users... kinda wish they would. But hey.
> At the moment if you join a channel you can't read its backlog, no.
Then I'm not entirely sure what you were referring to, when you said "IRCCloud can". Backlog from before you joined the channel is the specific feature that I was saying couldn't be done.
It's interesting to know that IRCv3 does have that support, so I was wrong about it not being possible. But if nothing implements it, it's not very helpful.
(You say "they're a client too" - I confess, I don't know what they are apart from a client.)