Phoenix 0.5 is my latest browser of choice, and it does not display the “reply window” properly on preview. It looks fine intially, but gets all scrunch when i preview a reply.
Mars: Mozilla does the same thing, too: Mozilla, Netscape, Phoenix, Galeon, and some others all use the same rendering engine called Gecko. Gecko is designed to be a portable rendering engine multiple browsers can build on, so every browser has the same level of standards-compliance and base functionality. There is a lot of information about building a browser on top of Gecko at Mozdev.
Derleth: They make heavy use of the deprecated Font tag.
Also, looking at the code, I see that the Img tag for the smiley has an attribute: alt="". While this does comply strictly, it sort of defeats the purpose of the alt attribute.