Sorry about that, it was a setting change that was set due to a number of former members emptying the contents of their posts. Basically, some members feel that if they're no longer going to participate in the site, then it's ok to blank all posts they've ever made. This makes all the threads they've posted in or started rather disjointed and confusing, and since we only store database backups for three days, we often don't notice this until it's too late to fix. Even if we do catch it, it's a tedious process to restore posts from a specific user. Most recently, a user who'd posted in a large number of threads opted to do this, which is when a change in settings became necessary.
Basically, the new setting prevents posts from being edited after about 2 days (60 hours). Long enough to allow anyone to edit a post in an active discussion, but not long enough to permit the malicious necro-edits we've had issues with. This setting has actually been in place for quite some time, apparently no one noticed until now (I actually kinda forgot I'd changed it).
Given the reasons for enabling this in the first place, I'm a little reluctant to reverse it, but I want you to be able to update that thread. Lemme ponder this with Mercury & others and see what we can come up with.