I think we're a lot more likely to get a negative rep or a signature if we massacre everyone in the room. Friends and family of the guards, embarrassed employers, etc all can be powerful enemies. If we limit the killing to an absolute minimum, we can claim to be "tools" of the nobleman's enemies; any additional killing is all on us.
Also remember that I was able to justify our presence to the F9 spirit using similar logic. If we start becoming butchers.. well, would YOU want to incur her wrath?
Once Inca posts his updates that get us into IP3, I'm going to cast Foreboding at the highest level I can. Probably get in the 7-8 hit range using Edge. That should take care of the guards. Then, depending on the circumstances, I'll either Levitate out or exit through the balcony using the spirit's Concealment power on the whole party.