Got k4 and k4.04 release15.1 (opensuse), both allow the font-size to be set, tried font-size:10px and 0.5em. The k4.04 on is a brand new install of opensuse 11 with nothing changed. Does the font-style choice make any difference?
I assume the 7 font size is 7pt? (how 7pt turns into 16px is pretty unlikely though) having a minimum font size in points kind of makes sense though, since users have different resolutions and monitors, making the minimum size a PHYSICAL measurement, is pretty logical.
Firefox has the same feature though. I have my minimum font size set to 16px because my screen resolution is huge. Some users on 800x600 screens will think 14px is big, but for those on 2048x1536, even 16px will be small to them. I do not want my eyes strained. You should never have to force a user to shrink their font sizes. Your text containers should always be scalable, by leaving them with default sizes, or if you must supply a width/height, use EMs, which scale with the text size.