I read somewhere recently that there were some spam bots posting logs on caches with links in that, if followed, took you to sites with malware/viruses in. This may be part of the reason for the change.
A good chunk of my logs are affected as my sig in c:geo posts links to the CC forum in BB code, plus I have posted links to here when appropriate, and links to other relevant places. From what I have just seen, my logs look a mess. If they had put just an ounce of thought into it they would of written a bit of code to convert the BB code lines to whatever they are using now. But no, this is Groundspeak we are talking about. They can keep my mess of logs, I don't have time to go through them.