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Date/Time: Fri April 17 11:53:25 PT 2026
ReportID: ID20260417115325
Name: Kuen-Bang Hou (Favonia)
Report Type: Report Error in Publication/Data
Opt Subject: Align UTS#51 & UAX#29 for flags and keycaps in ZWJ
UTS #51 and UAX #29 appear to be misaligned here. In UTS #51, ED-15a allows `emoji_flag_sequence` and `emoji_keycap_sequence` to participate in emoji ZWJ sequences via `emoji_core_sequence`, and ED-17 treats the resulting sequences as emoji sequences. UTS #51 further states that all emoji sequences are single grapheme clusters. UAX #29 likewise states that each emoji sequence is a single grapheme cluster. However, the corresponding default boundary rules in UAX #29 still rely on `Extended_Pictographic`. In particular, GB11 specifies `×` (no boundary) only for the pattern `Extended_Pictographic Extend* ZWJ × Extended_Pictographic`, while emoji flag sequences are handled separately by GB12/GB13, and keycap-based cases are not brought under the same `Extended_Pictographic`-based framework. As a result, some sequences now admitted by UTS #51 are not consistently treated as single grapheme clusters by the default segmentation rules in UAX #29. A previously discussed remedy was to change the `Extended_Pictographic` assignments of the keycap bases and `Regional_Indicator` characters, but no action was taken (PRI #453). Whether or not that remedy is adopted, I urge the committee to resolve this misalignment between the two specifications.