[Glyn]

Yes a system shield generator should prevent it.

It was done in a simultaneous PBW game, but it may work in non-simultaneous game if you managed to queue up your orders.
Try using all the ships movement ending on a star. Queue up the move to new system command and the command to go boom.

I don't recall ringworld or sphereworld saying that they prevent any type of stellar manipulation. The only reason they do is because it changes the object from a sun to a type of planet object.

We are talking about the two most advanced (research cost) peaces of technology in the stock game. It may be a bug, but it made for a very challenging & fun game.