I've only ever used Word under Windows, but I'm surprised you cannot change the font without altering the text. I'm more surprised that a font (Times, you said) does not follow the various standards, such as the ISO/IEC 8859 ones, which define character encoding.
Hang on, I've just had a look at Wiki (I'm not a wikipaedophile, honest), and in the article on Latin-1 it mentions that Apple came up with its own encoding scheme in 1984 which is "often a source of trouble when editing text on websites using older Macintosh browsers (including the last version of
Internet Explorer for Mac). However the extra characters that Windows-1252 has in the C1 codepoint range are all supported in MacRoman and except for the few missing ISO-8859-1 characters a Macintosh can send/receive files (and email) that are encoded/marked as ISO-8859-1 (with the C1 Control Characters) and Windows-1252 by remapping the glyph's codepoint numbers."
That might explain the thetas (although there's no mention of Word here), but I still find the problem with italics baffling. Then again, my background is Telecoms, where the control software is meant to work 24x7x365 and interfaces are supposed to be defined in standards (and even then, all is not perfect, before anyone asks!). It's a wonder any of this IT software works at all.
*Wanders off, muttering under his breath.*