Oh sorry, just saw this. I guess what I'm confused by is the fact that at some point I made an edit to the core app and that modification did (and does) persist.
... which is to say that if the system to revert changes has been around since... early June/late May, then I think I inadvertently found a way around it (that I admittedly can't replicate).
Since I can't reliably replicate the change, I guess there's no need to investigate or consider it further, especially if the code-reversion thing is a new addition (which would explain why I was able to modify my instance up until a few weeks ago, but not now). But I will +1 to the desire to be able to make modifications to core applications (even if we have to affirmatively take responsibility for crashing it, or at least have backups in place).
I realize the net balance of benefits vs costs might never support it though. In any case, thanks for the reply, I appreciate it.