“Dies: Do X
When this is put into your discard pile from play, do X.”
That really is correct. Dies is a shorthand that means went to discard from in play.
Things that are in play and then destroyed or sacrificed normally go to the discard pile, so that is the reason that “dies” applies. A hero that tries to go to discard goes to the command zone instead, and it still did trigger “dies”. A token that would leave in-play to go to any zone goes away. “Destroyed” seems an ok word to me. But no matter what word you want to use it’s gone (not “gone” as in going to the discard pile, but rather as in gone from all zones). A token that tried to go from in-play to discard “dies” (and also it’s gone from all zones after that). A token, or anything else, that tries to go from in-play directly to a zone other than discard did not “die”. For example, retuning a unit to your hand; that’s not dying because it’s not in-play -> discard.
If you would put a +1/+1 on a thing with a -1/-1 then those two runes cancel each other out. The card would then have neither of those runes on it. Can you cast Bloom on a card with no runes on it? Yes.