Specials

Interlinear annotation
Used internally for Japanese Ruby (furigana), etc.
`FFF9`	￹	Interlinear Annotation Anchor
		•	marks start of annotated text
`FFFA`	￺	Interlinear Annotation Separator
		•	marks start of annotating character(s)
`FFFB`	￻	Interlinear Annotation Terminator
		•	marks end of annotation block
Replacement characters
`FFFC`		Object Replacement Character
		•	used as placeholder in text for an otherwise unspecified object
`FFFD`	�	Replacement Character
		•	used to replace an incoming character whose value is unknown or unrepresentable in Unicode
		•	compare the use of `001A` ␚ as a control character to indicate the substitute function
		→	`2BD1` ⯑ uncertainty sign
		→	`1FBC4` 🯄 negative squared question mark
Noncharacters
These codes are intended for process-internal uses.
`FFFE`	█	<Not A Character>
		•	may be used to detect byte order by contrast with `FEFF` ⬚
		→	`FEFF` ⬚ zero width no-break space
`FFFF`	█	<Not A Character>

Interlinear annotation