Is there an obligation to mitigate damages?
Frequency/market practice: Very common; this is required by law for warranty damages (not indemnities), and is usually incorporated into purchase agreements.
Are provisions that there is no liability if the buyer has knowledge common, or does buyer knowledge have no effect?
Frequency/market practice: Provisions expressly addressing the impact of the buyer's knowledge as to liability are rare. However, when provisions of that nature are included, they usually provide for no liability of the seller if the buyer had knowledge.