Body cannot contain "??".
where in place of
?? the first used Chinese character appears.
Trying to add Chinese characters in comments results in
Comments cannot contain that content.
The first Chinese character is U+6587, which, according to Google Translate, means “culture”, so it doesn't seem to bear offensive or disputable meaning. If I remove it, the second character triggers similar messages. Again according to Google Translate, the sequence
U+6587 U+7AE0 U+5185 U+5BB9
simply means “Article content”.
I can paste the characters in the code examples in other program windows; the same if I try copying and pasting the characters in the resulting PDF file.