Power Gaming

It is considered a no-no to Roleplay another character's actions through your own actions. This is considered power gaming. If you are role-playing or dueling; it is best to say that you punch at the character, or thrust at them, or swing your blade at them - rather than saying that you hit them with your blade. There are a few exceptions, such as if you have spoken with the player of the other character before-hand, such as if you both had planned this as a "plot" or "event".

Example of powergaming: "Donovan throws a vicious elbow against Lionel's chin, shattering his jaw on impact and sending him sprawling to the floor."

Example of acceptable roleplay: "Donovan throws a vicious elbow toward Lionel's chin with enough force to shatter his jaw, send him sprawling to the floor, or both."

Obviously, it's almost impossible to account for absolutely everything. One could argue with a simple post like "Joe sits in a chair" because it doesn't give other characters enough time to pull the chair out from under Jim before he sits down. Of course, such a claim won't generally be made, but this simple example demonstrates that you won't be able to please absolutely everyone with your post. Just be sure that you don't take it too far, i.e. it's usually safe to assume that your character will successfully manage to seat himself/herself in a chair, but not if you cause a chair to explode and describe specific injuries dealt to the occupants of the room.