Far as I think about it, if one wants to hide a spell, they should pick up the subtle spell-metamagic. Making every caster able to do what is supposed to be a special ability (on par with doubling the range/duration of a spell) cheapens the ability and makes casters even stronger than they already are.
I takes a minute because it's not meant to be used in combat. I think for the power it has in the situations it applies, its very reasonable that it would be a spell requiring prep time and not one to just be popped of in the middle of combat.
If he doesn't know what spell you're casting, that means that he's even more likely to assume that you are trying to cast an harmful spell, making him attack you. And casting a spell takes an action, basically a third of your turn if you want, so the hobgoblin has at least 2 seconds to react, if not more. And thats plenty of time to stop himself from jumping.
Casting a spell and holding it uses visible components the hobgoblin could react to.
Incite greed also explicitly says that the creature avoids obvious harm while approaching you and does nothing beyond approaching you. If the would always run after the gem (forsaking personal safety to do so), this would be noted in the description.
I assumed it to be about weird interpretations/effects of spell that are either Raw but stupid (like find traps finding intentional clauses in legal documents) or common sense interpretations that still lead to weird outcomes (using bead of force+levitate+thunderwave to blast the BBEG into orbit). Because why make a video about people misinterpreting spells without making clear that this is unintended?
Depends on the amount work put into the magic systems lore from the DMs side. (I once wrote the ,,Theorie of magical trinity: Command, energy and will" and there's a lot of other work out in the internet as well)
I guess Heroes feast does not really count as cooking so...:
You could use wish and wish for the meal to be cooked perfectly
Mage hand is very helpful when you want to lift a hot pot or pan.
Since objects made by creation are real for the duration of the spell, you could create some food, it eat and even give your stomach time to... salvage the valuable parts before the spell ends
Clerics have a more elegant way to do that.