Yep, have noticed this also ! Sometimes it reverts back to a previously pinned currency when logging on other characters/accounts. *Edit* Another good reason to store these pinned currencies per character ?! Not that you need a reason to improve on something anyway, but it's a nice bonus :)
In addition, if you don't have a pinned currency on the toon you are currently playing, but you want to unpin it and pin another one, you can't unpin the one you don't have. Just had this happen with Seal of the Dragon for example. Should definitely be per character, or if that isn't possible for some reason, per account…
Agree @ OP. Looking at my shared bank slots (I know it's December '22 ;)), I see i still have some leftovers too ! Please allow for conversion to AD/RP/at least gold :pensive: !?!!