To explain what I mean first (since I don't know if there's a common term for it).

The following example assumes the player is mid jump, and presses the jump button before hitting the ground;

Basically it's so that if the player presses the jump button a few frames before they touch the ground, they will still jump. It's just something that makes things a little easier.

How do you feel about buffering the player's input when it comes to jumps? Do you do it yourself? Do you like it, dislike it? Do you think it has certain unforeseen disadvantages?, etc.

I think a bit of a buffer would be good, so timing doesn't have to be too precise. Maybe you would store their jump press for a fraction of a second, and if they land during that time it follows up with another jump. This way you could get all the responsiveness you want, without players accidentally doing extra jumps when they didn't mean it.

I mean, I already use it myself (and what you described is basically how it works). I just want to know what other devs think of it, since it's not something every platformer does, and I wonder if it's because some people have reasons not to (other than say, double jumps).

it seems reasonable to have it. Maybe connect the amount of time prejumps are stored to difficulty setting:

easy : store prejumps 0.3s

normal: 0.2s

hard: 0.12s

or whatever. Could make sense, you need to try it out in your own game.

Buffer might be a good idea, if it is very short.

But more important I think is to make sure the jump happens "whenever the character is on the ground and the button is down", as opposed to happening "when the button is pressed down, if the character is on the ground" (don't do it on button down event or whatever, do it as a check each frame)

That way, even if you press the button too early, as long as it is still down when you land, the character will jump.

You don't want the character to jump too long after you have released the button, I think that would feel weird, like your input is delayed.

If you don't want the character to be "bouncy" (that is, constantly jumping while you hold jump-button) then you could have a timestamp on press and only jump within a certain time after the button down event, if the button is down, or have a counter so it only can jump once.