Joining two multi-width chars should not involve a space

[lichray]

From email

last char first char behavior

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multi-width multi-width nothing ins'ed multi-width single-width 1 spc ins'ed single-width multi-width 1 spc ins'ed single-width single-width original

http://mail-index.netbsd.org/tech-userlevel/2017/11/06/msg010940.html

It's very unlikely we can find a language with visually wide characters but still spaced with single width spaces.