What happens to a HF (High frequency) electronic ballast fitting when you install a tube with shorted pins. Wrapping wire around the pins can sometimes bright a tube back to life briefly on magnetic gear. Will doing this on an electronic ballast cause damage?

It depends on if ballast have EOL protection 4 wire to the lamp, 2 each end.. i think it sense cathode resistant
from the cathode to run HF ocilator circuit putting HF
current on the lamp.  also at same time provide heating
current to the cathode.

2 wire to lamp Instant start HF is different that infact the ballast instructions tell to use Shunted sockets. so putting wire across the pins of tubes would serve no purpose as those sockets already shunted. these ballast
will hammer tube to vaccumme loss.

Most HF ballasts will strike tubes with open circuit cathodes anyway, no need to short the pins

Most HF ballasts will strike tubes with open circuit cathodes anyway, no need to short the pins

That is true only on the North American market, but not in the 230V world.
The "standard industry practice" in Europe is at least one filament continuity being used for controlling the ballast operation (either implicit on cheap ballasts due to the circuit topology not being able to operate without the filament connected, or explicit by the dedicated sensing circuit shutting down/restarting the ballast).
All that is to reduce the risk of an electric shock when only one lamp end is inserted and the other is touched (if the inserted is the cold end, so the one without the HV voltage, the ballast may start, but there is no high voltage able to ignite the arc, so the tube most likely stay in its not conductive state; if just the hot end is inserted, the missing cold end connection prevents the ballast from oparating, so no HV voltage is generated, so again the lamp remains not conductive)

By shorting the pins you may bypass that feature, but mainly on cheap ballast that will bypass the lamp EOL protection (= lamp filament in the resonant circuit acting like a fuse, which get blown open when cathodes loose emission and consequently the output resonant circuit builds up high voltage/currents) and so may fry the ballast as the result. And don't forget some ballasts use voltage mode filament supply, so shorting it may overload the filament circuit and so the ballast may fry as well.