Perhaps this is the case for you, but I it sound a bit like hyperbole.
To quote Tyll Hertsens who is very sensitive to sibilance:
"They're a tad bright for me (which means they're probably just right for most), but are not harsh sounding. (I liked them WAY more then the AKG K3003.)"
As someone who listened to both I found the K3003 harsher for sure.
Since Mr Tyll Hertsens "liked [the IE800] WAY more then the AKG K3003" AND Mr Sweden seems to agree with Tyll, I guess it's time for me to get rid of my AKGs and buy another pair of Senns.
Or perhaps I should wait until Mr Hertens declares the SE846 WAY better than the Senns...