I don't know whether this is common knowledge. I just "changed" my ticket to the exact same ticket on a long-distance sleeper, and got a $350 refund in the form of an Amtrak voucher, due to prices near Christmas having decreased from when I bought the ticket.

This seems to be a combination of three policies:

1. Amtrak has a temporary "free changes" policy for covid, with the caveat that you'll be responsible for any difference in fare

2. Surprisingly to me, if the new fare is lower, they will actually issue you a voucher for the difference, not only upcharge you for increased fares

3. Also surprisingly, you can "change" to the same exact ticket as the original one. I did this for a long-distance sleeper reservation, and it even kept me in the same room. This avoids needing to play 2-step games like changing to a new date then changing back to the original one. Just go through the change-ticket process, and select the same itinerary you already booked.

The upshot is: If you booked a ticket whose price has dropped, you can "change ticket" and get the fare difference back (as an Amtrak voucher).

It works for Acela Express trains too. I had a ticket for Presidents' Day week that was $154 in Acela Business (the only week when the fares were so high), but recently came down to $79. A few clicks, and I had a voucher for the difference.

I got two credit card refunds on a recent sleeper trip as the rate dropped twice. One of the refunds was within 14 days of the trip. Not sure what determines whether refund or voucher, but still a very nice policy.

Can this be done on an AGR points redemption? The points required for my trip went down, but when I use Modify Trip, Amtrak says I don't have enough points to buy the revised ticket (same date, train, roomette). Like it doesn't apply the value of the prior ticket to the new ticket, and credit me the difference. Time to call an agent ?

Yes it�s possible for AGR redemptions. Yes you need to call.

Update: I tried to do this recently, and the app no longer seems to allow a "change" to be the same exact itinerary. However, I was still able to get a refund when fares dropped by changing to an different train, then changing back to my original one. Slightly more hassle, but same end result.

I was able to do this as recently as last Friday, although it may have changed in the meantime. I did it a couple of times as the prices were fluctuating quite a bit.