DrDoc - 8:09 pm on Jul 17, 2013 (gmt 0)
I recognize that third party software is an exception. But, that also means they (those who wrote that software) simply didn't know any better.
Malformed HTML is really the bane of everything CSS to begin with. If the HTML structure is malformed, our best efforts at writing standards compliant CSS may be futile.
However, if the HTML is clean, validates, etc. -- we have, still, no excuse for using hacks, since conditional comments (as much as I dislike those, too) are a "clean" way of accomplishing the need, without having to worry about whether a hack will break in future CSS parsers.