The fact that Toph is still alive is not a spoiler.

The fact that Toph personally appears would be a spoiler, because it changes how we view Team Avatar and specifically Toph in the

Mainly because we can assume they are still alive due to information gathered earlier. But their personal interaction with the story may change how you view the story.

For instance.

Darth Vader trying to turn Luke evil isn't a spoiler, but the fact that Darth Vader is Abakin Skywalker and therefore Luke's Father is a spoiler because it changes how you view the story

Things that aren't spoilers.

• Ned Stark dies
• Dumbledore dies
• Tyler Durden attempts an anarchic revolution

These are merely story points, objective facts.

Things that are spoilers

• Robb Stark is betrayed at the Red Wedding
• Dumbledore is killed by Snape to prevent his suffering and save Malfoy from being a murderer
• Tyler Durden was a split personality