Is there an obligation to mitigate damages?
Frequency/market practice: Fairly common; additionally required by law.
Are provisions that there is no liability if the buyer has knowledge common, or does buyer knowledge have no effect?
Frequency/market practice: Fairly common; it is commonly requested by the seller for the buyer to provide for a representation that, except as disclosed in the agreement, it is not aware of any breach of the representations at the time of closing, but it is often resisted by the buyer. Also, it is very common for information fairly disclosed in the data room to release the seller from liability for a breach of operational or tax warranties (as opposed to key warranties, such as those pertaining to the title, capacity, solvency etc., which are usually not qualified by the knowledge of the buyer or disclosure).