why ‘book’ in custom fields not write in view key field

1
if you write ‘book’ in field key and value of custom field;
you can see the text only in the value’s field and not in the key’s value;
but on the site, bottom the post you re-see the name ‘book’;

idem if you write only this: ‘
why?
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2
next in the category’s field if I write ‘book’ in the item’s menu I see the ‘ not vertical but inclined.
why?
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3
in the field key, value, category is there problems for
sql inyection and/or xss or others problems?
are there more protection?