Using invisibility potions is generally frowned upon by players on the server, especially when a zombie uses one. During my time on the server, I have seen many players upset about the use of invisibility potions. I know that invisibility potions have long been a staple of this server, but they don't promote fun game play for the victims of invisibility potion users.
Other than removing the potions, I think it would be a good idea if they were nerfed in some other way. Like a raise in cost or further restrictions on their usage.