This character is a Símbolo modificador and is mainly used in the Greek script.
The glyph is a compatibility composition of the glyphs Space, Combining Reversed Comma Above. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+1FFE forms with similar adjacent characters prevents a line break inside it. The glyph can be confused with one other glyph.
El Wikipedia tiene la siguiente información acerca de este punto de código:
In the polytonic orthography of Ancient Greek, the rough breathing (Ancient Greek: δασὺ πνεῦμα, romanized: dasỳ pneûma or δασεῖαdaseîa; Latin: spiritus asper) character is a diacritical mark used to indicate the presence of an /h/ sound before a vowel, diphthong, or after rho. It remained in the polytonic orthography even after the Hellenistic period, when the sound disappeared from the Greek language. In the monotonic orthography of Modern Greek phonology, in use since 1982, it is not used at all.
The absence of an /h/ sound is marked by the smooth breathing.
The character, or those with similar shape such as U+02BBʻMODIFIER LETTER TURNED COMMA, have also been used for a similar sound by Thomas Wade (and others) in the Wade–Giles system of romanization for Mandarin Chinese. Herbert Giles and others have used a left (opening) curved single quotation mark for the same purpose; the apostrophe, backtick, and visually similar characters are often seen as well.