What 󠆅 means
It can select a glyph form only in a registered pair.
An ideographic variation sequence (IVS) places it immediately after the base ideograph, the written character being varied. The exact pair selects the glyph variant; selector number 150 has no fixed meaning across characters.
Why does the selector disappear?
It has no visible form on its own.
A proposal for ideographic selectors appeared on the Unicode agenda in 2001; the supplementary range was added in 2003 so plain text could request glyph differences without encoding every drawing separately. Adobe-Japan1, a collection of Japanese typeface glyphs, was the IVD’s first registration, on 2007-12-14. Unsupported or unregistered pairs display the base character and hide the selector, though the text can retain it.
Technical and specialized; it belongs only in a supported ideographic sequence.
Alone, it selects no defined glyph form.
Don't confuse it with
4Questions people ask
1Why does 󠆅 show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type 󠆅
󠆅\E0185Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.