The purpose of Q tags (defined in HTML 4.0 and W3C DOM Level 1) is to represent quotations more semantically, accessibly, and typographically- correct. Like many things, they haven’t caught on because IE didn’t support them.
Add this script to the head of your document to automatically sweep the page for Q tags in IE and display them properly (including nested quotes).
When (if) IE supports Q tags in the future, this will have to be updated with a browser version check.