We never heard of the black hole that delivered Nero to the past developing into anything much. Indeed, it seemed to be gone pretty quickly, or else a followup mission by Starfleet would have provided more insight into the phenomenon than our heroes in 2258 possessed.
Doesn't mean that a black hole fed with a diet of an entire planet would behave the exact same way, though.
"He beamed me here so that I could observe his vengeance."
Delta Vega had to be visible to the naked eye.
Heh. The very quote carefully avoids any reference to eyes or other visual means of observation...
For all we know it may have been visible to anyone on DV who looked up at the time.
That's highly unlikely, considering we met two people who had shared (that side of!) the planet with Spock at the time, and neither had any clue anything had happened to Vulcan. It wouldn't be something you'd miss if you blinked: Vulcan would be gone forever. And this would be left in its place: