One may suspect that other people are alt especially when the two accounts are connected to each other, but alt is allowed. It's just that you shouldn't use your alt to cheat a campaign that could get both of your accounts tagged.

You can even have more than one account as long as you can comply with the rules and norms of the forum that apply in the community, you will be safe because of it. But alas, many of them abuse their alt to greedily cheat campaigns so that they actually violate which will then only damage the reputation of the account.