you should be fine on Snow Leopard. the HSTS regeneration only happens on Yosemite, and Mavericks i believe.
test it out with this page:
http://www.radicalresearch.co.uk/lab/hstssupercookiesmake sure to enable cache removal in your Cookie preferences.
Thank you for the response. It doesn't even generate anything. Come to think of it, I tested it somewhere else and it gave me a unique number, but when I went back later the number changed so I'm not sure there are HSTS cookies possible in Snow Leopard with Safari?
Then again I'm also running Javascript Blocker, Adblock, etc. in Safari so maybe that's doing something to thwart it.