>> TL;DR: Despite otherwise seeming to work correctly, I can’t monitor a Back-UPS BX1600MI in Linux without seeing a constant stream of spurious battery detach/reattach and power fail/restore events that last less than 2 seconds each.

It sounds like the Windows software probably debounces the incoming events, only bubbling up those that are sufficiently time-stable, to account for bargain sensor false positives?

Edit: Looks like the apcupsd collection also has some EEPROM programming utilities... (for supported devices) http://www.apcupsd.org/manual/#configuration-directives-used...