Well mystery solved as to why the change happened, at least:
https://jira.secondlife.com/browse/WEB-474
Apparently, LL removed some functionality from their web based interactive map that some sites use, which broke their ability to show where on a map a postcard was coming from. (Breaking change # 1 with no warning). In response, Koz Farina who has some kind of in world blogging tool that relied on that functionality, requested that the information be added to the postcards that they could no longer get from the map.
Instead of adding another comment section to contain the new information, LL decided to just replace the existing one that has been constant FOR THREE YEARS and was added to the postcards at my request initially. (Breaking change # 2 with no warning). In other words, to accomodate their first breaking change, they made another breaking change.
Yoz Linden also included this wonderful statement:
"At present, the postcard format continues to be NOT OFFICIALLY SUPPORTED. In other words, we make no guarantees about all postcards being in this format, nor about the format never changing. If you write code that parses
SL postcards, please bear this in mind with regard to the assumptions your code makes, and the way it handles parsing failures. "
The thing is, this ultimately isn't even about the change. Change happens, and I can adapt. What is so annoying is the lack of any kind of communication about it. Why have the freaking blog if they aren't going to use it? Snapzilla is not the only site that uses postcards by any means. Developers supporting Second Life deserve better than this.