Before U19, It was possible to use these stones on other characters by dragging the stone into a hotbar before targeting them.
This is no longer the case, I now can no longer use a stone whilst another party member is targeted.
repro Old method:
1: /Invite XXX to party.
2: drag your Stone of Experience into a hot bar #1, slot #1.
3: press f2 to target your party member
4: press ctrl 1, then 1 to use the stone of experience on your party member.
Step 4 no longer works, it appears these experience stones are now self only, and may only be used by double clicking them within your inventory screen.
I have tried this today with an 8-16 stone of experience, and a 7-15 stone of experience, both appear to now work in a manner that is self only.
Had I known this functionality would be changed, I'd not have bought them in the first place