It provides examples. From these, we need to interpret items less directly covered. For example, can I cast a Lightning Bolt or Magic Missile on my erstwhile "friend", or stab him with a dagger, without ending the effect because "he's a friend"? I'd say no, but one can interpret the spell to say yes. Similarly, the Magic Jar effect allows the character on whom the spell was cast to attempt to possess a victim, a direct spell effect we agree is an attack. So the question is whether the intermediary step of entering the Magic Jar voids the attack's cancellation of the invisibility spell. I say it does not. That's not the only reasonable interpretation, but it is one reasonable interpretation.
Now, I had initially envisioned the Jar being on the character's person. If not, we have to also assess the prospect it is discovered and moved/taken. I don't see any likely discoverer recognizing its significance, though.
Let me put it this way: if an invisible Wizard possessed a friend's body (which is not an attack) and then attacks someone in that friend's body, does the invisibility spell on the Wizard's comatose body end?
If you are possessing him, the question first becomes whether that is an attack, another matter for interpretation. In part, the question is whether it is the wizard's physical form that must initiate the attack, or whether there is a link to the invisible person's animating spirit. A good question. My inclination is to consider the second possessed person a separate entity for purposes of the invisibility spell, but to consider "possessing from magic jar" to remain an action of the caster of the magic jar, and thus capable of ending the Invisibility spell. As I said, I can see wider or narrower interpretations both being reasonable.
I will invoke the "usually" part of that clause as it is not stated otherwise.
I believe the clause refers to Conjurations in general, not Creations specifically, which is why I am looking for other spells of that subschool. My quick search did not locate a convenient list. Summon Monster spells, though not Creation, provide you can direct them beyond simple attacks only if you can establish communications. I'm unclear what language a "quasi-real horselike creature" speaks. That would again suggest it is directed by its rider through reigns, etc.
Summon Monster also specifies your control over the creature. Summon Swarm indicates you do not. I'm not seeing a preponderance of evidence for any specific default. Nor am I convinced the "usually" is a default rule rather than a survey of the spells existing when the statement was penned.
I don't believe the interpretation the wizard can, or cannot, control the Steed is definitively correct. This spell seems to create a third possibility, that sometimes you control it and sometimes you don't. That spell seems much more fleshed out than Phantom Steed. It also imposes some added requirements on the caster (like being 7th level to cast this 1st level spell). The spell itself is merely "the final spell in the process of creating a bogun", so it isn't exactly indicative of a typical spell. An extended magical ritual ending with this and two other spells is required (one being Control Plants, which seems more likely to provide control).
If this is the closest we can find to a Creation spell that grants control over the creation, it would cement, in my mind, that such control does not exist by default, and needs to be specifically indicated in the spell.
In that case, I reiterate my previous point about that "usually, but now always" clause.
I reiterate mine regarding the lack of clarity as to the breadth of that clause.
What, in your opinion is reasonable for the PCs in game knowledge of XP?
Precious little, realistically. It's a metagame concept providing a measure based on activities that are prevalent in-game to determine results which arise from a combination of background (like research and training) and in game (like overcoming challenges) to determine when the GM should reward the players with an enhancement to their characters' power. Loss of xp tends to be described as a loss or weakening of life force, but gaining levels doesn't have that same connotation. It is certainly not "I am within 16 xp of gaining a level, so let's stomp and crash around the wilderness to attract a wandering monster we can kill so I can gain my level".
Keep in mind we live in a world with knowledge of quantum mechanics.
One which can neither prove nor disprove the existence of the soul, where people are killed by falling in their kitchen yet survive plummeting from an airplane. The real world is much more random than game worlds!
You will admit that it is a possibility that an animal which relies on its sense of smell to interpret the world treats people differently based on smell?
In any case, you have my roommate's story about her cats. For what that's worth. That is really all I can give you as someone who does not work with or study animals.
So, we have one anecdote that your friend believes that one of her two cats treats the other differently after it gets bathed, and maybe that's because you/she think that the shower changes its smell. Not exactly the kind of persuasive evidence I would hope for, especially when the link you reference makes it pretty clear the expert doesn't think a shower changes scent enough to make a difference to a creature who uses its sense of smell as a primary tool.
I would say that for point a, I am arguing that Prestidigitation can reduce one's scent so that one attracts less attention from natural predators. I am not arguing for invisibility to the Scent ability. The rules of the Scent ability do not allow weak odors to go undetected. However, an ordinary animal with scent but not Scent would be less likely to detect the wizard.
I'm not sure where you perceive the rules providing some intermediate step between creatures with the scent ability (like dogs, who even get a bonus to track, so they're better than most creatures with scent, or like cats) and creatures whose sense of smell is, like ours, weak and pathetic.
In that case, let me ask you a question: What part of "I can use divination spells to effectively gather information over wide distances, teleport the party to distant lands, travel across planes, and cripple enemies in combat with the same build" requires interpretation? And at what point is that on par with what Fighters do? (Which, if you will remember, is why Wizards are seen as overpowered.)
I find wizards are commonly seen as overpowered on the basis they can do all these things reliably, without fail, simultaneously and generally well beyond the terms of the spells. Teleport is especially open to such "beyond spell" interpretations. "Hey, let's go to a distant land I have heard of" versus "You must have some clear idea of the location and layout of the destination." (Teleport) and " you must have at least a reliable description of the place to which you are teleporting. If you attempt to teleport with insufficient information (or with misleading information), you disappear and simply reappear in your original location." (greater teleport).
Teleport is often merely a facilitator. We need to get to a far distant land in really short order to participate in the adventure. Luckily, the wizard had a Teleport spell, or we would have been months too late to defeat the enemy, or even participate in the adventure! Funny how this only happens when we have a wizard capable of Teleportation, or when we have access to some other means of Teleportation. If, instead, we must spend weeks or months travelling by ship or by horse, the urgency of accomplishing the next steps of the adventure are exactly the same than when we avoid that travel with a Teleport spell. The villain has never complete his agenda two days after our travels started, and long since moved on once we arrive.
And the typically forgotten aspect - you can't do all these things repeatedly, as the fighter can, so if the game does not (to use a much-maligned term) coddle the spellcasters by allowing them to go Nova in each encounter, then rest after one or two for a day so they can be fully reloaded, then they actually need to manage their resources, relying on teammates like the fighter who can keep delivering their combat abilities repeatedly.
