Gregory's Server@simevidas Some emojis (or Unicode characters in general) are actually a combination of multiple characters with a special "combine these" character between them (called a Zero Width Joiner).
This family is a combination of Man + ZWJ + Woman + ZWJ + Girl + ZWJ + Boy.
When you backspace you first delete the Boy, then the ZWJ, then the girl...
Also, HTML (or JavaScript) text length does not count Unicode characters, but essentially the storage size they take up.
@nifela @simevidas
Yes, an input field maxlength is supposed to count the glyphs but it counts the UTF-8 bytes instead.
I hope this is a browser specific bug and that other browsers are correct.