Original comment:

Here’s a fun fact: phone manufacturers know this. So what they call “100%” is not actually 100%.

My response, which was a small clarification:

That depends on the manufacturer, some do, some don’t. My phone has a setting to control the max charge, so I set it to 80% when I got it.

And the follow up from a different user:

Yes, but that 100% is not really that. It has been programmed to display that percentage, when i reality its 80%.

And my response:

No, I’m saying that not all manufacturers have that limit, and it’s a relatively new setting (last few years). If you have an older phone or something not from the top few manufacturers, it might not have that feature.

Then our conversation started. That's the context. Here's your first comment:

Exactly, which is neither a user setting or relatively new. Battery manufacturers have always had to decide what voltage is what state of charge (percent).

The user setting where you limit it to 80% is on top of what the previous commenter was describing

And then my response:

Sure, if the manufacturer sets it to not charge to the max. I’m saying some manufactured charge to the max by default, hence why that setting is useful.

My point is and has always been that this isn't universal, so don't just assume that your phone stops charging at 80% if battery longevity is important to you. Check if your phone does it so you can know.

If anyone is trolling here, it's you.