1) rooted my Desire with Unrevoked,
2) installed Auraxtremeginger 8.6
And then I'm trying to remove some system app with Root uninstaller... Failed.
I tried to create a new folder in /system/etc using Super Manager with root functions enabled... Failed.
I tried to do the same using ES File Manager... Failed.
I have SuperUser v188.8.131.52, Su binary 2.3.1-ef.
EDIT: OK, I managed to delete some stock media in the /system/media/audio folders. But I still can't create folders.
But it seems that I can't alter anything in the /system
*NOTE: All the above worked very well in Auraxtsense 8.4.