Okay, so, the explanation of this is a bit complex: Firefox renders textareas (like where you type comments and entries) in monospace font, while Safari and Chrome use sans-serif. The Foundation framework overrides that and specifies the same font used for the rest of the page for textareas, which means that in site skins that use a serif font (like Tropo) all three browsers will use the 'wrong' font (going by the previous behavior of textareas).

It's not possible to easily override the framework and tell it to go back to using the browser default behavior for textareas -- it can be done, but it's incredibly involved and not very future-proof. (We looked!) It is easy to specify a font that's different than the font that the framework uses by default, so we had to decide: do we go with the Firefox/Gecko-based browsers behavior of a monospace font, or the Chrome/Safari/Webkit-based browsers of a sans-serif font? Either way, it would be 'wrong' (not matching default behavior) in one set of browsers. (But that's better than being 'wrong' in all browsers, which is what the framework's out-of-the-box behavior is.)

Ultimately, I decided to tell fu to go with the monospace font (the Firefox/Gecko-based browser default) for one big reason: monospace fonts are generally rendered by browsers at smaller point sizes and perceived by users as less large, and given the consistent feedback of "the fonts are too large" that people have been giving us, right now we're taking every opportunity to mitigate that "too large" perception.

That does of course mean that people using Safari/Chrome/Webkit-based browsers are still seeing a change from default behavior, but we can't readily make it be default behavior in every browser. :( I'm sorry that it's causing problems for you, though. Maybe do a site-specific stylesheet to override textarea fonts to your preferred font? IIRC, Safari makes that easy.