(A) Please ask a confirmation on "menu" before dropping out of the game.
(B) Please allow voting to kick a too-long-idle player.
(C) Allow viewing of the help/tutorial in-game.
(D) Allow viewing of the help/tutorial in a non-linear fashion (change pages).
(E) Please speed up the dice rolling animation.
(E.A) The "who goes first" roll at the beginning can be completely automated -- there's no interaction, just skip it and randomly assign player order.
(F) Let you view your own/other player's player board/chip counts/etc at any time. I'd like to read my cards/plan my turn during other player's. I'm also confused regularly by other players' token counts and whatnot replacing my own in the corner.
(G) The two shield icons on dice are too similar and confusing. (One is shield with checkers, the other is shield with a foot?)
(H) Volume slider, rather than just mute toggle.
(I) UI widget for full screen toggle, rather than just alt-enter.
(J) Explain the purple die better.
(K) Linkify URLs in chat.

Also, the tutorial is missing some informations like, how to get those tokens one must spend on development cards.
And the game-length selector is easily overlooked by most people.