I think is probably OK if your employees are not active players of your game.
Otherwise, other players (your clients) will probably be upset because they are abusing their position to get advantages.
On the other hand, if they are "fooling around" in the game without actually playing it... I can tell you that is actually more common that you might think.
It's not unheard of that some "GameMasters" (employees of the company) have unique, overpowered abilities not available to everyone else. But normally it does not matter because they are not competing against players. It's actually pretty funny to be involved with them.
Of course, if they are doing it at work time, you can ask them to stop. But if they're doing it on their free time and/or after getting their tasks done, you can even ask them to help the other players. That way they get a break from work while at the same time they are building some sort of community in your game. Don't subestimate the power of having a community around your product.
My two cents as a former online videogame player.