According to Requirements for Chinese Text Layout (clreq) (discussed in w3c/clreq#716):
By default, the length of interlinear book title marks (type A) and proper noun marks should match the corresponding character frames. When two titles or proper nouns are adjacent, the adjoining ends of the marks should be shortened to create a visual separation, while the other ends remain unchanged. The shortening should not exceed 1/8 em.
As stated above, only the adjoining ends of the text decoration need to be shortened, whereas the current illustration (Figure 1) also shortens the non‑adjoining ends. Aside: Firefox 146 also implements the latter.

Figure 1 Current illustration for "text-decoration-inset: auto for <u>石井</u><u>艾俐俐</u>"
To address this, I have created a new illustration, shown in Figure 2. In addition to correcting the underline lengths, I have also highlighted the text boxes to indicate which parts are shortened and which are not.
Figure 2 The new illustration I created
Other related links
CC @fantasai @xfq
According to Requirements for Chinese Text Layout (clreq) (discussed in w3c/clreq#716):
As stated above, only the adjoining ends of the text decoration need to be shortened, whereas the current illustration (Figure 1) also shortens the non‑adjoining ends. Aside: Firefox 146 also implements the latter.
Figure 1 Current illustration for "
text-decoration-inset: autofor<u>石井</u><u>艾俐俐</u>"To address this, I have created a new illustration, shown in Figure 2. In addition to correcting the underline lengths, I have also highlighted the text boxes to indicate which parts are shortened and which are not.
Figure 2 The new illustration I created
Other related links
CC @fantasai @xfq