"Type keywords in the field labeled Click Here To Add Keywords in the Keywords area of the Keywording panel. Separate keywords using commas. Use vertical bar |, <, or > to indicate hierarchical keywords, such as animal|dog, animal > dog or dog < animal."
(Text to be added in italics.)
In Preferences > File Handling, it currently says:
That should be modified to:
"The vertical bar |, <, and > are automatically recognized as hierarchy separators."