When our users reply to comments in a ticket, the response gets added as a comment, twice.
The first time, just the email body is added and the comment is tagged with the "Reporter" label.
The second time happens up to 4 hours later and includes the entire email, including the email signature and is tagged as "Reporter" and "Internal"
I suspect some automation rule is possibly doubling up these replies but don't know where to start looking. I seem to recall seeing an option to strip linefeeds from email which might be a clue.