If you click on the “All Subscript Characters” link in my post towards the top, it will take you to the official Unicode list. At least half of them are for various phonetic alphabets (IPA, UPA) in which case each one has a very specific meaning / function. Then, in the “Superscripts And Subscripts” block (20 of them), the Unicode Standard (the actual publication), states (Version 12.1, page 829):
In general, the Unicode Standard does not attempt to describe the positioning of a character above or below the baseline in typographical layout. Therefore, the preferred means to encode superscripted letters or digits, such as “1st” or “DC0016”, is by style or markup in rich text.
and:
A certain number of additional superscript and subscript characters are needed for roundtrip conversions to other standards and legacy code pages. Most such characters are encoded in this block and are considered compatibility characters.
and:
Standards. Many of the characters in the Superscripts and Subscripts block are from character sets registered in the ISO International Register of Coded Character Sets to be Used With Escape Sequences, under the registration standard ISO/IEC 2375, for use with ISO/IEC 2022. Two MARC 21 character sets used by libraries include the digits, plus signs, minus signs, and parentheses.