The big problem with twists like these...

If you know they're coming, it sort of ruins the surprise. If the GM asks if it's okay to have party betrayal (or if someone else asks and the GM says yes) then you're constantly on the lookout for it - because why would they ask if it was irrelevant? Of course, nothing says the GM can't ask an irrelevant question in the same manner they keep irrelevant minis next to their screen, but it's something that's usually frowned upon (what amounts to non-consensual PVP), so if it's known to be ok, you'll be looking out for it and then the twist won't stick.

Of course, if you don't know it's coming, then it's never a place your brain will go. You aren't just going to accuse a character (and thus player) of working against the party because that's a heavy accusation. It carries a lot of weight behind it since you're only a few steps down from calling someone a problem player. Players often don't have a good enough grasp on other players' characters to notice behavioral shifts, and players often don't have good enough acting skills to roleplay them correctly.

I've yet to hear a story where someone figured this kind of twist out before the reveal, and that doesn't surprise me at all.

But by no longer utilizing poison against the party because of the monk, the monk has effectively made the entire party immune to poison by virtue of it no longer being present in encounters! Hah!

But seriously though, cutting out stuff you know the party will hard-counter is just going to make the party not feel as cool. A balance of both is important. Believe me, as the guy in the party who could cast Silence, I know; hard-countering every boss encounter kind of makes the boss feel lame instead of fun.

Not quite the same, but a Paladin in a campaign I was in once bought a Shield of Missile Attraction for cheap because the shopkeep thought it was cursed.

Well, aside from the fact that it already looks blurry...

Most AI image generation is inherently unethical, for multiple reasons. That's not necessarily something to do with the visual quality of the image, but it's lumped under all the reasons to hate AI image generation that are all collectively stated under the pejorative "slop".

Such is modern slang.

At times like this, I regret that I am bound by the ancient Orcish custom of not giving a damn about what Humans think of me. But you'd better believe that if I wasn't an Orc, I'd be bashing your head in!

It's 3000 GP just for the material components, plus another 400 to pay the caster. At one gold piece a day (the amount a skilled artisan earns) it'd take 11.5 years to earn a clone with a poor lifestyle (2 SP per day).

So you're living a poor lifestyle for basically half your professional life, just to earn the ability to repeat your professional life and spend another 11.5 years of it earning the ability to repeat your professional life just to spend 11.5 years of it earning the ability to... you get the idea. You'd also need to find a caster capable of casting an 8th level spell, which is rare.

Possible? Yes. Popular? I doubt it.

A clearer way to phrase it might be "there are no rules for the genre of fantasy". An individual world needs self-contained rules, yes, but just because Tolkien's Dwarves have beards regardless of gender doesn't mean that your Dwarves need to be the same.

Wild magic Sorcerer: I do not control the Lobsters (they just kind of showed up)

That's better communicated through... communication.

I don't know about you, but if I were playing a game to win and my "opponent" reveals that they can just cheat and instakill me whenever they feel like, I'm more likely to just stop playing the game than to try to play it for fun. Even if I did try to play it for fun, it would be hard to really enjoy it when I know that any encounter can just be a big middle finger.

If you don't explicitly tell people what they're doing wrong and how to fix it, it's unlikely that they'll figure it out on their own.

You check the label and realize it actually says "Tenser's floating Dikc", but the salesman is already gone.

Arcane Dye - for when you don't want to worry about mixing your whites with your reds.

Healing Ward - blocks all heal effects on the target.

Heap Metal - for when you don't feel like paying a hireling to collect the gear of that bandit camp you just slaughtered.

Antilife Spell - wait, I guess that's just Power Word Kill...

Burning Lands - when Fireball just isn't Fireball-y enough for you.

Chromatic Orc - summons an orc ally. A different color each time you cast the spell.

Control Hater - a more powerful version of Command that only works on things that are currently hostile to you.

Fire Stork - that wizard must have really hated storks. Incinerates the nearest stork.

Fig Cloud - an alternative to Hero's Feast for vegan parties.

Glyph of Barding - acts as armor for your horses.

Prismatic Ball - hold on, I've been notified this was just a mistranslation of Chromatic Orb. Never mind.

Rope Brick - this is what you get when you let the Barbarian make spells.

Sheep - conjures a sheep.

Stonespin - does what it says on the tin.

Runbeam - force the target to move their full speed every turn.

Rime Stop - I was kicked from a table after bringing this into a Rime of the Frostmaiden campaign.

Wash - why would you spend a 9th level spell on Prestidigitation?

In my eyes, the Rule of Cool is best used as the opposite of the Air Bud Clause. (For those who don't know; the "Air Bud Clause" refers to a rule in basketball that basically says "it's not allowed just because there's no rule against it".) TTRPGs are imperfect systems, and you are going to run into a scenario that isn't covered in the rules. Rule of Cool is best used here, rather than to bypass rules that do exist.

But also; some systems can be really crunchy, and a lot of the time it can be more fun for everyone involved if you just say "you know what, that's cool, let's do it" than to pause for five minutes to leaf through some rulebook (because seriously; you can't always know the entire rulebook by heart) trying to determine if and why they can't.

Of course, doing this too much is dangerous. Hence "in moderation".