Certain strings involving Unicode characters where the printed character length is less than 20 characters, but the byte length is more than 20 bytes, will not be accepted by the forums.
five→five→five→five→five→ works, because both lengths are more than 20
five→five→five→five→ doesn't work because the string length is 20 but the byte length is 24.
12345678901234567890 works, because both are exactly 20
1234567890123456789" doesn't work, because the string length is 20 but the byte length is 21.
The error is:
Database reported: ERROR: value too long for type character varying(20) .
Failed query: INSERT INTO search_words (word) VALUES('1234567890123456789"')