Bit of a slow news day, eh? In that case, have this matchmaking table; since MM tiers were changed for 5.9, this is what tiers of ships can get matched with other tiers:
There was a change on the test server that made all carriers have +1/-1 matchmaking, but it doesn’t seem to be reflected here. I don’t play carriers often (sadly), certainly not high tiers, so I wouldn’t know personally. If you’re a carrier player and you’re, say, not getting into tier 10 games in your Shoukaku, do leave a comment! This is something I’ve not found a definitive answer to, and I’d definitely like one.
edit: well, it didn’t happen on live.