Why is it that the villians have no compunction killing Superboy/Superman? True, he's trying to stop him, but they should know Superboy/Superman is really important to their history, given how he's saved the universe a number of times in the 20th/21st century/ Especially Legion villains born on Earth, who's premature killing of Superman would have a far more damaging ripple effect.
Maybe they think it's a different guy?
Quite possibly. How much has Superboy really announced that whole "I'm the real thing from the past and need to get back there alive and well or the entire timeline falls apart!" deal, anyway...and how many supervillains would be the sort of person to believe that even if word got around to them?
On the flip side, what are the Legion of Superheroes thinking when they send Superboy into the future for youthful hijinks? Even if it's a small chance, he could die and thus unravel the time-stream.
If Brainiac 5 is so smart, can't he make Wildfire a containment suit that looks and feels more like an ordinary human? It would sure make things a lot easier with Dawnstar.