In 3E, the charmed person considered the caster "a trusted friend and ally"; furthermore, "it perceives your words and actions in the most favorable way" and "might be convinced that something very dangerous is worth doing"
All of these sound more like a friend than like an acquaintance.
The spell description for 3.5e is self-contradictory. The very first sentence is "the charm makes a humanoid creature regard you as its trusted friend and ally (treat the target's attitude as friendly, see Influencing NPC Attitudes, p.xx)." Friendly is a defined attitude in 3.5e (and 3.5e doesn't say anything about acquaintances, I would assume by definition most friends are Friendly), defined as "wishes you well" and will "chat, advise, offer limited help, advocate." Friendly creatures will not take risks for you, for that you need to change their attitude to Helpful, defined as "will take risks to help you", and will "protect, back up, heal, and aid." The fluff of Charm Person more closely matches Helpful, but it is very clear in stating that the target becomes Friendly, not Helpful. When I run into a contradiction between the stated mechanics and the fluff, I usually side with the defined mechanics. Charm does set you up nicely to attempt to move their attitude from Friendly to Helpful, but it takes some time, effort, and a successful Diplomacy check on top of the effects of the spell.
It also required opposed charisma checks to get the target to do anything they wouldn't normally do, like say a kobold showing a human their hatchery, or a devoted castle guard letting someone through who doesn't have approval. I have good friends where I work, but if they ask me to put something into service that hasn't been approved, I'll still tell them "no" despite the fact that we are good friends. Charm Person doesn't make the target stupid or an automaton, just friendly and willing to give the benefit of the doubt (I would say gullible, but I think that is too strong). A charmed McDonald's cashier probably won't give you free food, but he will tell you that getting a McDouble and adding special sauce and lettuce is cheaper than a Big Mac for effectively the same thing. And while it says that a "charmed fighter might believe you if you assured him that the only chance to save your life is for him to hold back an onrushing red dragon for just a few seconds", the "might" implies it's going to take some convincing, and just because he believes you doesn't mean that he is going to actually try to hold back the dragon.
Also, there is a difference between knowing what you did and knowing that you were charmed. If a trusted friend said, "Could you drop this package off for me?" and you did it, in 2E (but not in 1E or 3E), you knew that the friend asked you and you knew that you did it. You didn't necessarily know why you did it. You just felt like it. In 5E, you knew why you did it, because you were charmed. Substantial difference.
Nothing in 3.5e prevents the victim from knowing what happened while they were charmed; nowhere does it mention that the victims memories of the time are wiped or altered in any way, it just doesn't explicitly state that the victim remembers everything like 2e does.
But after the fact they no longer consider the caster a close friend, see no reason why they would have considered the caster a close friend, and are no longer under any compulsion to view any interaction with the caster in a favorable light. There is nothing preventing them from understanding that they weren't actually friends with the caster, that they may have never met them before, or that they might not even know the caster's name. The magic that clouded their thinking is gone. The situation is akin to the person who just realized that the person who was claiming to be a long lost relative was actually a scammer who took advantage of them. How strongly they react to that is going to be a factor of how significantly they were taken advantage of, losing their life savings is going to elicit very different reactions than just paying for lunch. They don't need to understand the mechanics of how they were taken advantage of to know that they were played. 5e does weaken it by letting them know outright they were charmed, in earlier editions if you were careful you could be subtle enough in your interactions that even once the charm was gone nothing was so egregious to cause major red flags.
Definitely nerfed. Downgraded from someone who considered the caster a close friend and might risk his life, to somebody who considered the caster a friendly acquaintance where social interactions are viewed favorably and after the fact knows he was charmed.
And if you notice in my original reply, I categorized Charm Person as notably weaker than earlier editions. I agree with your assessment that it was nerfed. I just don't fully agree with your take on some of the fine points of how it worked in earlier editions. It may just be a difference in how the game was played at our respective tables, Charm Person was always ruled on the conservative side in games I was involved with, particularly in the 2e days since it was such strong effect with a potentially unlimited duration, castable by a first level mage for the same cost as a magic missile. If it were to be ruled on the liberal side, the logical in-game consequence would be that the spell would be widely banned and any caster found to be using it would be subject to summary execution before they attempted to use it to take control of rulers or other people of significance, or even attempted to take over an area by just charming dozens of people (average commoner would get a save every 3 weeks, and would need a 19 to save). Mid and high level mages were already overpowered relative to other classes without giving mages the ability to have their own free army at level 1.
