First off, I would like to thank Meredee for mentioning Xathen.

Was not an easy task bringing something like that into PS without everyone raising hackles.
Secondly... RP'ing is what sends PlaneShift apart from virtually every other MMO out there. I think this has been stated plenty of times already, but it sets the frame of reference.
Now, I'm in total agreement with everyone who's said RP-bouts need to be done in a mature manner. What I have noticed, and what hasn't been mentioned yet (that I've seen) is the different styles of RP'ing a fight. I submit for your review the three basic types I've observed:
-The Blurb
-The Clinical
-The Novelist
Blurb writers are of the type that
Marqsaynt mentioned, except sans dice. Brief post, not terribly descriptive, and often difficult to envision the battle. But my only real dislike of this method is that often, it turns into an RP 'race' as each duelist tries to speed-post and gives his opponent no time to react. I'm sorry to say that it was just such a fight that gave Kieve his first taste of RP fighting in-game.
Clinical writers are more of the sort Kaerli mentioned - writing out exactly what happens with precision. Easy to envision, but without the 'flow' of combat. This approach might be best against folks who OOC'ly don't want their characters to fail, since it seems to force a distancing between player and character as you sit back and examine each move. Akin to sitting up in the booth, watching from the stands as your avataars go at it. Or maybe that's just my experience.
The Novelist, the category I tend to fall into, writes too damn much. XD They try to account for and reply to each move with a writer's finesse. It makes for fine reading, even in log form, and helps draw you
in to the battle, same as reading a book would, but with its own drawbacks - namely, the fighting moves at a snail's pace. Posts come slowly, and require a lot of reading at each round, not to mention that it can be easy to miss something if you're not careful (which opens itself up for OOC arguements).
I'm not about to say one is better than another, necessarily, though I do have my own preference. Yes, we all have our own opinions about PVP (in either form, via RP or mechanic), but for my part I find a roleplay environment to be a writer's landscape - and in that context, may the best writer win.
