Standardly, dropped threads/logs will not count for AC if they do not meet the 4 response limit as we are looking for responses, and not completed threads/logs. If the thread is dropped, but meets the four response requirement (unfinished posted log/non-complete marked thread) the player is welcome to use it. If someone is having trouble with this, and the player can reasonably show that they are trying to make up the activity, the mods will be willing to consider alternatives to pass AC. However, the idea of "modly consideration" is for this to be an outlying factor, and not the norm. If constant considering starts to become a factor, the mods reserve the right to refuse further consideration.
The example you provided with the 3 responses for one character and 4 responses for the other, this interaction would count for the character who had 4 responses, but not for the character who had 3 responses, once again, because we are counting replies, and not if the thread/log is completed or not.
Thank you and please let us know if you have any additional questions! Emi Mods~