By this logic Crossroads Gossiper shouldn't trigger when he's ressurected by Redemption since the card has already been played when he comes to life. Guess what, it does trigger.
I agree. Every other card I can think of doesn't trigger off of the effect that summoned it.
This specific one is because Crossroads Gossiper has an "after" timing trigger, and not a "when" timing trigger. You're right that it's a bit of an edge case, because there aren't many interactions like this. But part of Redemption's effect is to summon a minion. If that minion is Gossiper, then Gossiper is on the board before Redemption "finishes" casting. Then, since Gossiper is already there, it checks to see if any friendly Secrets have been revealed. Redemption has been revealed, hooray! It's buff time.
If Gossiper had a "when" or "whenever" trigger, its check would occur earlier in the sequence. Specifically because this is an "after" effect, Gossiper can gossip about themselves. ("Oh my Yogg, can you believe I died? For real. Totally dead, but I'm like, back now. Seriously.")
I think we all know this by now. The way obtained deathrattles work is not intuitive either, but we know now that having obtained a deathrattle at some point is different from being a deathrattle card.
Also, don't pretend like the game is always consistant, and that every interaction makes sense: I just tested playing Twilight Geomancer with C'Thun in my hand. C'Thun is now technically not a "taunt minion", but rather obtained taunt from another card before he was even played. Bulk Up, Into the Fray and Feat of Strength should not buff him, right? Guess what, they all do.
In this example, your specific C'Thun, at this time, IS a "taunt minion." It was granted the Taunt condition by an external force, yes, but it is both in your hand and has Taunt. It is, therefore, temporarily a Taunt minion, even if that condition is not intrinsic to the card. I'd be interested to see whether Hadronox would resummon him under these conditions. I would expect him to, because C'Thun, specifically, is an exception to a lot of Hearthstone's usual zonal rules. Since C'Thun's buffs are all worded as "wherever it is," those buffs are persistent in a way that Mok'Nathal Lion's is not.
You can discuss word order and context until the cows come home, we all know that overloading a mana crystal regardless of how it happens should trigger unbound elemental. Anything else is just a level of nit-picking from team 5 that is not evident anywhere else in the game. Shamans have it hard enough without this bullshit.
Hearthstone does differentiate between "An X card" and "When Y occurs," and it has done so for years. True, there are a relatively small number of examples of these interactions, but they do exist, and they are meaningful distinctions.
I agree that Unbound Elemental ought to have its wording changed to function more like Tunnel Trogg (in activation condition, but not buffing for each crystal Overloaded), but as it currently stands, Unbound Elemental not triggering from Guidance is correct according to the wording.
Guidance is in fact a card with overload, so by the wording Unbound Elemental should trigger. But that just one of M A N Y bad wordings and oversights from these useless developers :)
In the same way that a Corrupt card is not the same as a Corrupted card, simply having the word "Overload" on a card does not mean that playing that card is "Playing an Overload card."
To use a different example, Crabrider now gains Windfury from a Battlecry. So it is a Rush card (so it will continue to gain buffs from Parade Leader and be in the pool for Athletic Studies and Stage Dive), and it is now a Battlecry card (so it can be discovered from Blazing Invocation). But, despite having the word Windfury printed on it, it is no longer a Windfury card, so it won't contribute Windfury to Corpsetaker.