@Kabensaal, what we have here is a classic notion of applying OOC information to IC scenarios.  

[quote]Hey! You think you can get away with killing me that easily?!" he yelled at the huntress-in-training. "What? Did you think they'd just let anyone guard the entrance to the Dragon's Den? My semblance allows me to heal all wounds. Basically, I can't die![/quote]

This does not whatsoever indicate that the bouncer's weakness is being lifted off the ground.  Sure, he said that he heals, but he didn't say how he heals.  He didn't even say his name, so on the off chance that Antaeus exists in the RWBYverse, and Mokuren knows about it, she still wouldn't know to apply that to this guy in this instance.  Setting up a situation for Guess to reply to rather than autohitting him was a good move, but even planning to exploit the bouncer's (unknown) weakness counts as metagaming.