Seems like there is a lot of flip flopping by the Devs on this though. In my example of the black horse; mine were deleted back when it was a "fresh exploit" but to
@MalagAste point people have them now-a-days and it's no big deal bc they are considered "rare". I don't know enough to speak on it personally but I think the glacial stuff also falls into this camp. I've heard some glacial stuff has been deleted but then I see glacial spellbooks on auction... so who knows.
Think it just depends on the "mood of the day" as to what gets deleted and what gets ignored on any given day or moment... and who the GM is and what their interpretation of the "rules" is...
I know back when they had UOWeddings and you could buy the "Wedding" package which included RL wedding certificates and such... along with a set of engraved rings... we were also given the opportunity to a name change adding a "lastname" so to speak...
Well, when Willa married Polynikes we were both given the last name "Of The Yew-Wood"... Which was just fine for several years and then one day while we were at an event Poly gets pulled away by a GM who informs him that his name is too long and not allowed and his name was then changed to Polynikes of Yew... which we both were sort of mad about... Now technically Willa's name is still to this day 2 letters "too long" for anyone to duplicate... but I guess there was a difference between her name at 2 letters and his at 5... Willa's name has never been changed but I did ask Mesanna about it years ago when she fixed my personal bless deed to actually recognize my character ... and she told me that NO no one should ever be allowed to change my name as I did pay for that... and to let her know if anyone tried. So she remains Willa Of The Yew-Wood... But Poly never got the rest of his name back.
As I said I think it just is the "flavor of the day" sort of thing as to what is or isn't allowed at any one moment.