Salem

Do bears can destroy fences easly in claimed area? If we will have braziers, will they attack bears when they hit fences?

no / no

but they can stun you by using stomp even if you are on the other side of the fence.

At least about a week ago bears could aggro and use their AoE/ranged attacks through a fence.

Yup, bears are pretty mean since they can still fear-attack you through your fence. Always try to AFK in Boston to avoid getting accidentally killed by a bear when on your claim.