This Unicode Standard Annex will be updated for Unicode 7.0. The proposed update is now available for general public review and comment.
The exception list for SpacingMark has been updated for Unicode 7.0. That list excludes specific characters from being assigned the Grapheme_Cluster_Break property value SpacingMark by default.
Please see the PRI page for details and instructions on how to review this issue and provide comments: http://www.unicode.org/review/pri265/http://unicode-inc.blogspot.com/2014/01/pri-265-uax-29-unicode-text-segmentation.html