Actually, the scenario was much simpler than that, to do with building dynamic HTML where form fields could contain characters like apostrophes.
It turns out that apos; is not a named entity in HTML4, but is rendered as the single character you might expect by both Firefox and Chrome. However, when we ran into IE not rendering it "properly", it turned out that we were wrong, and IE's behaviour was perfectly legal. (Whether it is standards-compliant to render a non-standard entity in this way, I don't know; the point was that it turned out not to be IE that wasn't compliant at all.)
I think I see now, you mean that as ' wasn't in the HTML4 spec despite the other browsers all rendering it consistently as an apostrophe MSIE not rendering it was not a breech of the standards.
So MSIE was compliant but just backward about it's approach to things that were beyond the standard. This presumably wouldn't ahve been an issue at all is MSIE supported XHTML ... but I digress, thanks for responding.
It turns out that apos; is not a named entity in HTML4, but is rendered as the single character you might expect by both Firefox and Chrome. However, when we ran into IE not rendering it "properly", it turned out that we were wrong, and IE's behaviour was perfectly legal. (Whether it is standards-compliant to render a non-standard entity in this way, I don't know; the point was that it turned out not to be IE that wasn't compliant at all.)