There are very different philosophies on when moderators should remove any content. Most Stack Exchange sites are on one side of the extremes with rather low barriers for deletion. Especially comments are often removed at the first sign of trouble.
Some communities fall on the other end of the spectrum and almost never remove content unless it is extremely offensive or spam. The users in such communities often feel strongly about this, and removal of borderline content is viewed as censorship.
My impression as a moderator on one of the most strictly moderated SE sites (Skeptics) is that the ability to simply remove comments is extremely valuable in preventing conflicts from escalating. If a conversation is getting personal I tend to nuke comments immediately. This often prevents any escalation as at that point both sides don't really care enough to continue, at least as long as there is no previous bad history between the users.
What I've observed in other communities that have strong opinions against removal of content is that small-scale conflicts between users can escalate and lead to very long threads of aggressive posts and a rather toxic atmosphere.
What preventative measures can be taken to avoid such escalations if simply removing non-constructive posts is not possible?