If someone has two accounts and if they apply to two different campaigns then I am okay with it.
But if they apply in the same campaign with both accounts then I am not fine with it, however if I know their accounts then I will accept one for the same campaign.
If I don't know that two accounts were owned by the same user but later found they were accepted in the same account and they did not let me know even in PM to keep it private, I will tag both accounts.

I hope I made my stand clear for joining multi account in the same campaign.

For your information, the forum allows anyone to have unlimited accounts.