I'm sort of a worry wart. If I had a glow plug with a bad tip I'd be all about getting it out before it broke off and killed a piston and head. I've seen much worse than the picture LMLLover posted. I'd rather have it break inside the cylinder and then go get it than leave it in question. That scope makes it real doable. Even without the scope I'd go ahead and do what it took to get the glow plug out. If it left some debris inside then I'd go after it with a small magnet until I could piece the glow plug back together with no pieces missing.
But that's just me.