PROBLEM: When I edit the css and increase border thickness: save, preview: no effect; it ignores the change (because the thickness setting's pre-empted by the system config. setting? --could I place an important tag in the css and get around this?).
Doesn't matter whether the vcard template's on or off--this css setting gets ignored.
Yes you can use !important in a css statement to force it to overrule all others. Example:
border-width: 10px!important;
Also, sometimes when you change your CSS files it does not seem to reflect on your site because the old style is still cached. You can force a site refresh by hitting CTRL-F5 and this will usually reload the CSS changes.
Also noticed that sometimes the vcard template source window goes totally blank. Does it get corrupted or what? (Ok I'll ask about this in sep. post!)
The actual file is probably not corrupted but all I can say is that anytime something weird happens while viewing the vcard template DO NOT SAVE IT! I learned this the hard way

ONE related problem: the editor window works fine for css revs and retains the formatted source code. But not so for the vcard template. I can't scroll down to view, as it immediately contracts to one wide line. Is this normal? When I toggle-editor, formatting's lost and jammed together. Hence I paste into & from a text editor to revise.
This only happens to me when I am using Opera browser. Not sure how to remedy this otherwise. It's never occured while using Firefox or IE. Maybe check your javascript error console? Are you using the default admin template?