About a checkme in 3.1.2

[xfq]

https://www.w3.org/International/clreq/#glyphs_sizes_and_positions_in_character_faces_of_punctuation_marks

Solidi should be vertically and horizontally centered within their square frame. In GB rules, it should take 1/2 em, whereas in Taiwan, there is no clear rule about its dimensions but most publications will give them the same dimensions as a single character.

分隔号位于字面正中，中国大陆的国标规定排版时占半个汉字的大小；而在台湾则未有相关的规定，但多数出版品使用一个汉字的大小。

1. "within their square frame" should probably be "within the character frame".

2. "it should take 1/2 em" should probably be "it should take 1/2 em in horizontal writing mode".

[xfq]

Fixed the first point in https://github.com/w3c/clreq/commit/47f2589e57c0526983e9812653ee1df0e845f8cd

The second point will be discussed in #623.

Closing.