The default snapcompact frame fonts (X.org 8x13 for every provider, plus the selectable 6x12 and legacy 5x8) drew digit zero as a bare oval visually indistinguishable from letter O. Image-based compaction OCRs the frames back, so 0 and O were mixed up and compacted identifiers (e.g. Slack IDs) got corrupted.
Zero now carries a disambiguating interior mark the O lacks: an ascending slash in 8x13 and a center bar in 6x12/5x8. unscii-8 (8x8/6x6u shapes) already shipped a slashed zero and is unchanged.
Fixes#8713
roboomp
70af5c300b