TIL that GitHub search only indexes the main branch! Didn't need it this time because you told me what branch to look in, but now I know how to efficiently search across branches for future reference thanks to this StackOverflow post; for instance, I could have found the file I was looking for using the following command
# Search all files and folders in all remote branches
git branch -r | awk '{print $NF}' \
| xargs -P "$(nproc)" -I {} git --no-pager grep -n 'setupTagline' {}
Here's the relevant file, if anyone's curious:
Might help to know where you found this, if possible. The character you pasted is in Unicode's Private Use Area, so it's not a standard character, and that's why it's not rendering properly on Hexbear—no standard font is going to have a corresponding glyph to represent it. It could be an archaic form or even a neologism, but I'm by no means an expert in either PUA usage nor hanzi/kanji so I'm just spitballing here.
edit: the specific codepoint is U+E00E, for what it's worth