When you disagree with something someone on LJ has posted on their personal journal (i.e. not a community), and you feel like venting or commenting about said disagreement, the appropriate place to do so is:
I'm posting this poll because, as you can see by the instructions on my journal, I always assumed that one's personal LJ is one's own safe free-speech space, and that it's extremely bad form to come and beat someone up on their own journal, thus leading to the conclusion that people can appropriately vent on their own journals but not on other people's.
However, I've recently noted several instances of people getting very upset because they had some disagreement, conflict etc. with another party who then posted about it on his or her OWN journal. I've seen some people post comments like, "You're a chicken, a jerk, etc. to slag me in your own journal instead of on mine where I can see it quicker." As this is the polar opposite of what I think (someone who pitched a big disagreement with me in my own journal would get questioned and then, if they kept it up, dropped or banned), I was curious as to what everybody else thought.