Superscript and Subscript Characters in General Use

[Marcel Schneider]

Is there any other reason not to use superscript characters for 
abbreviations in plain text? (Except those reasons already 
discussed, that sum up in the compatibility issue when it comes 
to rich text.)
(Same question for subscript digits for vulgar fractions, that may 
be considered a kind of abbreviations:
- 'Page two of seven' is represented as 'Page 2/7';
- 'Two seventh' is (or should be) represented as '²⁄₇'.)

Iʼm asking this question now as long as this thread is not closed.

Iʼm not in the habits of asking many questions, but perhaps this 
one I should have asked.

Marcel