Hi !Hubzilla Support Forum
I've encountered a bug when trying to reply to someone with a text containing Unicode (apparently 4 bytes). I was using the mobile site and added an Uniode emoticon using my Android keyboard. There was an error message something about a "System error". After enabling the debug log, I saw this:
SQLSTATE[HY000]: General error: 1267 Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE) for operation '='
SQLSTATE: Invalid datetime format: 1366 Incorrect string value: '\xF0\x9F\x99\x82 @...' for column 'body' at row 1
After removing the emoticon, the post when fine.