Seems the file corruption issue no longer occurs after these reallocation events as well. I'll keep watch; will have to get a replacement HDD if it gets nearly bad enough.

On another note, my main webserver OS drive (where this very microblogging instance is hosted) actually has 14 reallocated sectors from the original 0 over the years... and the original issue was a stuck UNC that a zero-write cleared (and the bad sector count remained at 0). That was back in October 2011, when the server was migrated to Linux.