I tried in IE8 and IE9 and they render the same as Calibre, Chrome and Safari, so it seems that ADE is perhaps the odd one out. However, the scaling applies to the inherited font size and I would have thought that ADE was actually right since this is the way that CSS usually works, and nesting other tags, (body,blockquote,div,p,span), does lead to such scaling! I don't know why tables should be exempt from CSS inheritence, (all properties or just some?), but there seems to be agreement between many rendering systems that this is correct.
So, can I do anything to get ADE to render in the same way or should I avoid using tables and find some other way to line up columns of data? For example, do readers support the CSS width property with <span> elements?
Update: I wonder if tables are treated differently due to the possibility of nesting them, which would result in progressive scaling of the font-size with each nesting level?
Update2: It seems that there is more to this than meets the eye! I found some useful information about this, (and other 'quirks'), at
http://www.quirksmode.org/css/quirksmode.html