The HVCC was implemented to prevent Lenders, Loan Officers, Mortgage Brokers, Real Estate Brokers, Reators/Agents, Buyers/Sellers and anyone else from influencing an appraiser and/or the appraised value of real estate. The emails as you described, violates the HVCC, USPAP, Realtor Code of Ethics, Appraisal Ethics, and may be considered appraisal fraud, real estate fraud, and/or mortgage fraud.
If you follow thru with the transaction, it is my opinion you may very well be taken advantage of by the agent, appraiser and possibly the lender (loan officer/broker) by possibly paying more in the purchase price, more in commissions (which are factored into the price), and other transaction fees and/or costs.
The purpose of the HVCC is to create a separation between a loan officer or loan originator (loan broker) or sales agent (Realtor) and the appraiser retained to value the property.
With limited exceptions, the HVCC calls for no contact between the lender or sales agent (Realtor) and the appraiser regarding the property being appraised. Compliance with the HVCC became mandatory June of 2009.
I suggest you to discuss the matter with the agent's Broker before closing your transaction.
If this is a short sale: I always talk to appraisers for short sales. Agreeing that the place may be worth $30K more, well, I don't know what to say about your agent, but I do know that the appraiser is giving a RANGE value back to the bank and it's funny that you / she used the exact amount of $30K, because that's exactly what they're reporting.
They need to report back to the bank with a value range of $30K more & $30K less ("30 up & 30 down"). If the appraiser hasn't turned in their report yet, just make sure your agent strongly suggests to the appraiser that the value should come in at the middle mark, which represents $30K less than the high end value.
If it's not a short sale: I would advise against agreeing with the appraiser about the value being $30K higher, but then again, the value could really be $50K higher, if the seller needs to sell, they may just let it go for less.