Even English doesn't fit in ASCII! English is often used as the justification for ASCII—by technical types anyway. To use “only plain ASCII text” would mean constraining oneself (no dashes or paired quotation marks, for example). Many English loanwords are accented (outré or soupçon) as are some personal names (Zoë). Some uses of italics are considered mandatory even beyond emphasis, such as when writing the title of a work (The Art of Plain Text).

Restraining the textual representation of English to ASCII due to imaginary technical limitations is ridiculous.