Disguise Self to 0 height

Question

Assuming one's character is 1 foot or smaller (either naturally or through some other ability, e.g. Alter Self), and then use Disguise Self to [...] seem 1 foot shorter [...], would this character effectively disappear?

As an illusion, it would not change the physical aspect (the character would still exist in the same 3D space), just how the character is perceived. But other than that, how close of invisibility would that be?

Socially, how would you handle that situation - like an invisible character?

In combat, what advantage would this gives? Full cover? Advantage on attack and/or defense? Sneak attack?

Alter Self:

Change Appearance. You transform your appearance. You decide what you look like, including your height, weight, facial features, sound of your voice, hair length, coloration, and distinguishing characteristics, if any.

Disguise Self:

You can seem 1 foot shorter or taller and can appear thin, fat, or in between.

PHB 195:

When you attack a target that you can't see, you have disadvantage on the attack roll.

When a creature can't see you, you have advantage on attack rolls against it.

Related: Question Regarding Disguise Self and Height (Reddit)

Answer 1

1 foot less than 1 foot is 0 feet. It would not make you invisible.

A character that managed to do this would just look flat.

When attempting to Hide your DM gets to decide what is a valid hiding spot. I wouldn’t read Disguise Self as doing anything other than “seeming” to modify your height, so it wouldn’t help you hide. With Alter Self you could become flat, which may help you hide somewhere you otherwise couldn’t. Similarly you may be able to be blocked by cover more easily. Other than that, there is no benefit in combat.

Socially you would draw a lot of attention for your strange appearance. Again, this would be up to the DM whether you are regarded as a curiosity or an abomination.