Black Square Button on Facebook

What it signals here

reaction meaning

Not commonly used as a reaction; occasionally used in comments as a filler or to create formatted text blocks.

comment use

Sometimes used by users trying to create visual separators in long comment threads.

boomer interpretation

Likely interpreted literally as a button or icon reference, possibly confusing to older users.

group use

Used in group posts as a bullet-point alternative or decorative separator in announcements.

See it elsewhere