Space between characters after joining two lines

Background of this issue

Something like the following paragraph in an HTML file:

Here is an English paragraph
that is broken into multiple lines
in the source code so that it can
more easily read in a text editor.

will become:

Here is an English paragraph that is broken into multiple lines in the source code so that it can be more easily read in a text editor.

when rendered in a web browser, i.e., lines are joined and one space is added between two lines.

However, in CJK text (except Hangul), the spaces are not added. For example:

这个段落比较长，
用一行写不行。最好
用三行写。

becomes:

这个段落比较长，用一行写不行。最好用三行写。

when rendered in a web browser, i.e., there is not space after ， and 好.

Question

The CSS Working Group would like to know which characters should not have spaces around them when joining lines.

Here is the current list, categorized using Unicode blocks: https://drafts.csswg.org/css-text-3/#space-discard-set

The interesting questions remaining are:

• Bopomofo (the spaces should not be discarded per https://github.com/w3c/csswg-drafts/commit/e56978ecc12165ab7059902fdaa89230ef2cff53 and https://www.w3.org/2020/05/07-clreq-minutes.html#t08 )
• Yijing Hexagram Symbols / Tai Xuan Jing Symbols / Counting Rod Numerals
• Enclosed CJK Letters and Months / Enclosed Ideographic Supplement (the spaces should not be discarded per https://github.com/w3c/csswg-drafts/issues/4992#issuecomment-652213888)
• Chinese and Western Mixed Text
• Punctuation

Unlike fantasai, I'm leaning towards not having spaces for all three categories above. WDYT? @w3c/chinese-layout-req-contributors

See also (CSSWG issues)

• https://github.com/w3c/csswg-drafts/issues/337
• https://github.com/w3c/csswg-drafts/issues/4992
• https://github.com/w3c/csswg-drafts/issues/4993

Start by reviewing the CSS Text Level 3 space-discard set and the linked CSSWG issues, then examine the unchecked categories: Yijing/Tai Xuan Jing symbols, mixed Chinese and Western text, and punctuation. Done means reaching agreement with the Chinese layout contributors on which characters should discard spaces and documenting that decision.