One of the Solar goals is to foster a learning environment, a place for mentoring and collaboration. Therefore, we strive to be polite, courteous, and cordial when talking with other members. If we can't be constructive, or can't find some humor, then we prefer not to say anything. At least then other developers won't think we're jerks (and yes, what they think is important).
To paraphrase Robert Heinlein: in any machine, you have to grease the moving parts so they do not grind each other to bits. In the machine of civil society, formal courtesy is the grease that keeps the people from grinding each other to bits. Argumentation is acceptable, discussion is dandy, but deliver no insults and display no anger or impatience. Among other things, this means no "sighs", "grrrs", and no passive-aggressive sarcasm.
We're all working together here, and the closer we get, the more friction there is guaranteed to be, so the more important formal courtesy becomes. Thus, be nice. :-)