Hello, I'm not exactly sure where to post this, but I was wondering if running two accounts and performing the exact same action simultaneously is considered against ToS or not?

I have run into a situation where a player on my team was controlling two characters in a PvP instance at the exact same time. I recorded the player and it is clear that the player was either running a script or abusing some sort of bug that allowed him to run actions on two accounts at the same time.

If this is against ToS? Where is the appropriate place to report this and how can this be prevented in the future?