Incivility

Uncivility : use of personal attacks, name calling, never-ending insinuations, lies, defacement of personal pages, accusation of vandalism, call for banning toward another wikipedian.

This style of interaction between a wikipedian and another wikipedian tend to transform participation on Wikipedia, an unpleasant experience for the wikipedian victim of the incivil behavior, as well as for the whole community.

When and why does that happen ?

In case of an edit war, when people support different opinions, or for power sharing
When the community grows big. An editor do not know all the others, he may not perceive their individual importance in the project, so do not feel like preserving bonds that do not exist. Reputation do not count so much.
Sometimes, a specifically impolite outsider unfortunately gets in the projet

Why is it bad ?

because it makes people unhappy (resulting in discouragement and departure)
because it makes people angry (resulting in non constructive or even uncivil behavior themselves, further escalating the uncivility level)
because people lose good faith (resulting in even less ability to resolve the current or the next conflict)

An example of escalating incivility

Uncivility happens for example when you are quietly minding your own business, and an asshole tells you "If you're going to write a pointless page, you could spell check it".

Removing uncivil comments.

striking offensive words or replacing them by milder ones on talk pages
removing offensive comments on talk pages (they stay in the history however, anyone can find them back or refer to them later on)
deleting a whole edit made by the offenser (require technical help)
delete permanently an offensive comment made on the mailing lists (require technical help)
replace a comment made in a comment box by another (require technical help)
revert an edit with &bot=1, so that the edit made by the offender appears invisible in recent change (do-able on ip contributions, require technical help for loggued-in user)

Preventing uncivil comments to enter the wikipedia sphere or reducing the impact

prevent edit war and conflict of persons (unlikely, these are constraints set by the project itself)
compensate each uncivil comment by providing a soothing comment
preventing the access of Wikipedia to some class of people more likely to be offensive (reduce openness)
force delays between answers to give time to editors to recover and avoid further escalation of conflict (temporary blocks in case of conflict)
Just do not read the offensive comments. Do not answer. Forget about them. Do not escalate.
Make as if the offender does not exist. Set a wall between the offender and the community.
Revert edits with a veil of invisibility (&bot=1) to reduce the impact of the offensive words when made in comment box
offer feedback (praise the ones who did not answer to uncivility by uncivility themselves)
play on negative feedback (let an editor in conflict choose to leave wikipedia, whether the offender or the one cible of the offenses, to reduce risk of conflict)
apply peer pressure (voice your displeasure each time uncivil words are used)
solve the root of the conflict between the offenser and the editor (or the community)
set a new rule based on word usage, that will allow temporary blocking or banning an editor using them more than xx times
filter mails by the offender, or filter mail based on some key words, and reject an email to the mailing list when offending
consider that uncivil words can't be avoided in such a project, and accept their existence.