I speak about particular feature: player-configured item protection. This IMO really meant to protect valuable item - not to do something else. Halting potential unsafe cases leading to item loss. In this context, I can imagine allowing trades of these with "friendly" players can be okay per se - but only as long as they marked as such.
I just checked: The NPC in question asks you to confirm the action AND the confirmation option is not the first one
This makes selected item exposed to ARBITRARY SCRIPT CODE! Whenther particular code does something destructive is really up to server's scripter and um, how do you even foresee what they could/would do in future? This feature not meant to depend on what server side does, "prototype" also been 100% client-local thing.
As for other pro made MMORPG... in real world players DO use >1 account. Even if this formally prohibited in some places, enforcement is laxed unless it causes measurable problems, like someone lacking common sense and e.g. using heal bots, getting unfair advantage over others. Ofc like this GMs would kick in and try to resolve situation, but other than that... why more populated server or potentially more money are something bad?
You could make another one with a dark mage character in it and you would feel the item protections getting in the way 
Would rather try to get resonable items on that char to not bother with all that shuffling. Once in a while I can even manually confirm some operations. Not a huge tragedy for something I do once in a months. I.e. I would optimize frequently used cases, this not going to be "frequent action" on my side regardless of # of accounts.
P.s. on funny note, do you know you can in principle bulk-store and bulk-retrieve items (storage <-> inv) even w/o coding this in client, by rather dumb script sending chat commands via IPC? Funny thing about M+ is: quite many actions - even those in menus - are in fact "chat commands". And thus one can have quite decent automation for "exotic" cases via IPC.