I was going to suggest you could configure a PM style sheet but then did some testing and realized we don't have a set style for replies. They all seem to hardcode <font size=2>. Could we add another tr style (tr.reply_body perhaps) to make this part of the interface configurable as well?

I don't know how much effort this would involve, I just thought I'd throw it out there. Thanks.

Update: fixed the <...> tags in the first paragraph.