Board Thread:Speculation House/@comment-26417457-20190715232011/@comment-35199716-20190730125122

Mouseyboy221 wrote: Yeah, we need at least one more fight with Ruby and Emerald. Ruby or one of the heroes can learn that when Em uses her Semblance, she has to remain standing. This probably won’t happen to at least Volume 8. I think they figured that out in Volume 5 since she kept spamming it in her fight with Ruby, but of course that was all offscreen (Fuck the battle of Haven, seriously we saw like none of the fights apart from 3 second glimpses every now and then before it cuts to the only people not fighting and standing around talking).

There's also her outburst where she summons the giant salem illusion that everyone saw, so they all probably know.