Look at Matt's and Lunar's posts at the end of page 4 and beginning of page 5. When Matt wants to make himself a suspect, Lunar gets spooked and chooses to instead implicate himself. Then when we all accused Lunar of being the murderer, he just posted" I have no idea what you're talking about." Which is, thanks to cliche', as good as a confession. The real kira killer would never have given up.
Sounds like he's covering for someone, and I think that someone is Matt. If we kill Lunar now, Matt will kill again. I change my vote to Matt.