@zerocontext, RiotAether, whoever works on the new live client or can forward this - On chatrooms
They're physically too small and ten lines of text (assuming message is not is longer than ~40 characters, then it takes up two lines, if not more) are not enough to keep up with a fast conversation with 8-9 people actively taking part in it - or even half the number if the matter requires actually longer, in-depth responses, that break into multiple lines. Note how chat joins also take up a line, which means more now than it did before.
Despite old pvp.net client being flawed in many ways, that was not one of them.
You've requested feedback so here it is - please either make chatrooms resizable, or double/triple their vertical size for a significantly more comfortable experience. There is no downside to doing so, given how much free space there is on top of the currently sized chatrooms.
Cheers.