but in the later BtS patches that rarely happened.
I call B....inaccuracy. With a heaping helping of experience (and other player testimony) to back it. Civs could and would peacevassal before they were even willing to talk! Maybe on lower difficulties it wasn't such a problem.
Worse yet, once you did take a vassal, it made the GUI LIE TO THE PLAYER. Not mislead. Not give a slightly inaccurate picture. Lie. Here's what happened:
1. Civs would display a -1 "we are upset about rivals being vassals to your empire". So far, no problem.
2. SECRETLY, the game would average the AI's disposition towards you and towards your vassal, and round it down. In other words if they were pleased with you and cautious to your vassal, they are now cautious to you, though you will never, ever see this represented in game. This happened completely independently of whether you helped said AI in that war, and independently of all visible diplo displays. Your +19 friend could declare on you because they were -3 with your vassal and were actually cautious, lulwut.
3. Just to make sure everyone can actively and objectively see this is a broken feature, they made the same averaged-to-hate-you AI still vote for you in diplomacy as if the averaging DIDN'T take place

. In other words, the same AI that suddenly dislikes you for having a vassal it hates will STILL vote you to win the game outright! But er...only if you get lucky and it doesn't declare. Does this sound like a sensible thing Firaxis did on purpose? Anyone want to dare biting on this and actually arguing that it's sensible

?
Don't even get me started about capitulation logic -----> people who know this logic well literally can't deny it's a broken system under the hood.
- Having a stronger military presence makes them less likely to capitulate sometimes? Check.
- How badly you're dominating them being irrelevant as long as their power is above average? Check. (You can literally have 6x they're power and have killed 30 units and they're doing fine on their own).
- A completely useless vassal that happens to border your target makes your target more likely to capitulate, even if it doesn't kill a single unit. That same vassal not sharing 8 border tiles or more? Actively HINDERS capitulation.....
- Vassal power does screwy things to power evaluations for free civs declaring war.
That was an extremely fun feature, sorely missed in Civ V, where the very notion of long-term friendship has become a bad joke.
News flash: that notion IS a joke. In a game where only 1 winner is possible, any friendships are in fact short-term alliances, formed by smart players against other blocs to increase their own victory chances over factions that don't do so, but with both understanding that they'll eventually have to duke it out themselves. What such temp alliances do is significantly increase the odds of the eventual winner emerging from that bloc; standard theory suggests something like 1/4 of the possible factions involved IIRC.
If the game had permanent alliances, we could talk about "long term friendship".
Regardless, vassal states were NOT indicative of long-term friendship. It's one side bending the other over, either through war or because someone decided to essentially throw the game.
You don't get a vote when you didn't even know what we were talking about.
It seems he felt he was presented enough evidence to conclude that it was never a working mechanic; however we now also have points made that it wouldn't fit well in V's model anyway. A DoF is a better theoretical mechanic than straight selling yourself out anyway, not to mention the actual fairness in rule application.
I don't think it's going to be easy for anyone to make a strong case for a feature that objectively never worked well and doesn't fit the model of the current game, especially given a somewhat sorry state of diplomacy existing already.
And the difference from a Civ surrendering and giving up all but a few cities to be puppeted by victor?
Minimal? Also irrelevant. By putting vassal states down, I'm not supporting idiot AI behavior or king-making in civ V. The quoted statement has no relevance to the OP at all.
By the way, puppets are generally taken directly, not gifted over (it takes a lot more beating to get the AI to let go of cities in deals these days, they might take it even further that direction). Unlike vassals in many ways; you can have control over those cities easily at any time as long as they're well improved or you have 600 cash on hand that isn't going into CS or RA.
Vassal system was superior because the subject was still competing

.
subject could break away if master hit on hard times and access to subjects resources was not a guarantee.

. Seriously? Actual civ iv experience shows that the master pretty much never lost control of a capitulated vassal, and if it DID (via master getting its butt kicked), it didn't bode well for the win chances of the vassal. Care to give a fair estimate of cap vassal win odds in civ IV? I'd put the over/under at 1%...with the only vassal chances being a very broken AP win (as bad as vassals are, that thing is even LESS thought out, GJ there Firaxis X_X. Try testing expansion features sometimes!) and the rare culture win where the master decided to lose on purpose by taking capitulation and then actively defending its vassal so it could lose. Hardly good situations, either of those.
By the way, despite how utterly broken the AP was, take a look at the patch history since BTS release. It makes Firaxis/2k look awful. As broken as civ V has been, track record for these patches is (so far) better.
Peacevassals were even worse. The AI used them like we can use making a resource sale and then breaking it through tile pillage/swap now. Bend over, accept techs from the backside, break free, bend over, etc...possibly using one's empire body for some good old war bribes on top of taking techs up the backside. You'd think the vassalings would get sore! Nope. What perplexes even more is the master behavior in this situation; you can't make a serious case that AI treated peacevassal as anything but a permanent alliance, and you never will be able to do that. However, that amounted to a
simple conclusion; someone sacrificing their victory for the other. In other words,
Kingmaking.
Mandatory flamebait line: Puppeting is a for all intents and purposes a dumbed down vassal system.
Not-quite mandatory flamebait response: This assertion suggests a lack of understanding of the strategic choices of the vassal system, the puppet system, or both.
If anything, the vassal system more closely resembles city state alliances, except that in civ V city states start off with different rules as an entity as the major players and their "kingmaking" is actually determined by objective investment of resources. There are LOTS of ways civ V is inferior to civ IV, but I don't think you can make a realistic case this is one of them. City states/puppets look a heck of a lot better than RNG king-making with AIs not even trying to win, using utterly convoluted under-the-hood mechanics that the vast majority of the forum still doesn't know.