Appreciate the replies!
Sadly it does seem 3rd-party apps are the only option. Incredible that MS chooses to display an active second hand on the left-click pop-up clock from the taskbar and also digitally displays the seconds in the Time & Date properties tab but disallows this option in the persistent clock.
Anyhow, even though I was searching for a very minimalist option T-Clock 2010 had me enthusiastic until I noticed it has no auto synchronization (a fairly important factor for my usage). The next best utility I found for adding seconds to the system clock is 7+ Taskbar Tweaker - 7+ Taskbar Tweaker - RaMMicHaeL's Blog
. While it does have fewer bells and whistles (preferred) it doesn't designate yes or no for auto-synchronization. If I get an affirmative reply from the developer I'll inevitably give it a go as it looks to be the best option...so far.