Since the Wikipedia: space has a page labeled Wikipedia:Civility that uses the {{policy}} template and Category:Policy category it's logical to think Wikipedia has a civility policy. Unfortunately, this isn't entirely true.

Wikipedia has a vague civility meme that folks wave in the general direction of when behavior doesn't meet their personal expectations. The evidence is conclusive:

Throughout the project, breaches of the expected level of decorum are common. These violations of the community's standards of conduct are unevenly, and often ineffectively, enforced. (1,2)
— English Wikipedia Arbitration Committee

A truly civil, collegial environment would not tolerate the use of Facepalm Facepalm in discussions and "sighs" in edit summaries.

An society which professes claim our goal is to leave banned editors with their pride and dignity intact and then insist on Scarlet letters such as {{banned user}} isn't the epitome of civility.

This is not to say the Wikipedia is an alt-usenet anything goes environment; disruptive / offensive behavior by folks clearly not here to contribute are generally dealt with quickly without fuss. It is to say that when tempers flare between content editors disagreeing while improving the encyclopedia, how we address that is ... complicated.