When I tried to change the comment overrides for another user of mine who uses S2, I saw that I couldn't select the button "Override" for the text of comment links. There was a little question mark icon next to the grayed-out option linking to FAQ 145, which further links to FAQ 131 on the benefits of paid accounts.
However, FAQ 131 does not mention the ability to select comment link overrides as one of the features of paid accounts. I suggest it be added (perhaps after "Ability to create custom styles and have exact control over your journal's layout"?)
(I was especially confused since my first encounter with S2 was on DeadJournal, which allows comment link overrides in S2 styles for free accounts, and I assumed it was the same on LiveJournal.)
Hm, picking a different S2 style (Clean and Simple rather than Tabular Indent), I see there are a bunch more options which are not settable and which have the little question mark icon: size of page border, preferred font in a couple of places, and style of lines around day headings.