Just in case, someone is faced with this problem. Some points worth knowing:
IE Mobile 7.5 reports a false value for the font. So you are out of luck with this feature with Modernizr.
To confuse issues, it also ignores conditional comments for IE Mobile, as suggested above. It actually picks up conditional comments for IE9. The only way I could fix it was to add a conditional comment as follows:
<html class="no-js" lang="en">
And then the prefix of the corresponding styles with the class .ieMobile75 . If you want these styles not to get into the IE desktop, I would suggest combining them inside a media query.
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