Up front -this isn't a complaint about UI blocking while under the influence of these powders.
But I do notice, that if I am typing in chat, when someone tosses sneezing powder (i think, we're under a fun filled powder assault in the project streets as I type) that the chat box loses focus, and I i don't notice it I wind up triggering a whole bunch of in game windows because I stopped chatting and am then hitting what the game thinks of as a flourish of keyboard shortcuts (l, m, etc). this part is more of a pain then funny and could probably be dealt with just by ignoring the keyboard input in that state, rather than the UI element losing focus.