The most interesting question raised in my opinion is Bruno essentially saying that thread-per-request blocking I/O server design is safer than event based server design. If one thread dies it's less likely to propagate problems that will kill the server. Due to this added complication he thinks that node.js should focus more on reliability and believes that V8, with roots in browser side and not server side JS, is ill-equipped.
Jason wants to focus on two things. First, he keeps asking for specific examples of where problems have arisen (as otherwise it appears to be a theoretical fear) and second he wants to push node.js towards 1.0 and stabilize the API and feature set.
It seems Jason thinks Bruno is looking too far into the future. It's essentially the architectural equivalent of premature optimization - until the API and feature set stabilizes there's not going to be any great call for perfectly reliable production servers.
Even then Jason is confident Joyent can deliver on the latter considering how many active V8 devs they have working for them.
Both guys seem to really love server side JS and want to push for it, they just have different ideas about which direction to head.