Internal Server Error while posting smile in issue's description
It took a time to realize why issue's creation throw Internal Error.
It turned out that text was actually copy-pasted to description from somewhere and it contains smile.
I can't provide full text because of privacy but here is relevant error from log:
Processing by IssuesController#create as HTML ..skipped.. Completed 500 Internal Server Error in 130ms (ActiveRecord: 67.5ms) ActiveRecord::StatementInvalid (Mysql2::Error: Incorrect string value: '\xF0\x9F\x98\x8A\x0D\x0A...' for column 'description' at row 1:
Relevant article to fix issue.