when one shows mercy icly and pretty much get burned later for trying to put story/rp/experience/continued antagonism in the future for all, over 'winning'... Well, it does tend to put a person off future interactions, and it's hard knowing that you might be trying to play fair, but the other guy is not. What is 'fair' is rather subjective of course but some situations are clearer than others.
That's why I personally do talk ooc before the antagonism or CvC conflict even if it doesn't lead to physical altercation, because the drama ought to stay ic, yet so very often there's more drama oocly than in for such actions, I don't consider that worth the rp.
I have a lot of respect for players who have Garda characters, who are behaving entirely ic, yet get more ooc drama than ic reactions to what happens as a result. It's quite possible to be oocly supportive of the Garda faction and what they add to setting yet still 'hate them' ic.